nuxtでgenerate時にルートに動的ページが生成されてしまう

Nuxt.jsとWP REST APIを利用しSSGのブログサイトを作成しようとしています。
nuxt.config.jsのgenerateで/posts/_idに動的ルーティングできるよう設定したのですが/_idのページも同時に生成されてしまいます。

原因として考えられるものがあれば教えていただきたいです。

js
1//nuxt.config.js
2
3  generate: {
4    fallback: true,
5    routes() {
6      return axios.get(process.env.API_URL + '/posts?_embed').then((posts) => {
7        return posts.data.map((post) => {
8          return {
9            route: `/posts/${post.id}`,
10            payload: {
11              posts: posts.data,
12              currentPost: post,
13            },
14          }
15        })
16      })
17    },
18  },

pages
   |-index.vue
   |-posts
      |-index.vue
      |-_post.vue

console
1✔ Generated route "/posts"                                                                                            23:42:28
2✔ Generated route "/posts/3642"                                                                                       23:42:28
3✔ Generated route "/posts/3584"                                                                                       23:42:28
4✔ Generated route "/posts/3442"                                                                                       23:42:28
5✔ Generated route "/posts/3580"                                                                                       23:42:28
6✔ Generated route "/posts/3677"                                                                                       23:42:28
7✔ Generated route "/posts/3548"                                                                                       23:42:28
8✔ Generated route "/posts/3424"                                                                                       23:42:28
9✔ Generated route "/posts/3610"                                                                                       23:42:28
10✔ Generated route "/posts/3595"                                                                                       23:42:28
11✔ Generated route "/posts/3600"                                                                                       23:42:28
12✔ Generated route "/"                                                                                                 23:42:28
13
14 ERROR  Error generating route "/3600": This page could not be found                                                  23:42:28
15 ERROR  Error generating route "/3642": This page could not be found                                                  23:42:28
16 ERROR  Error generating route "/3595": This page could not be found                                                  23:42:28
17 ERROR  Error generating route "/3610": This page could not be found                                                  23:42:28
18 ERROR  Error generating route "/3580": This page could not be found                                                  23:42:28
19 ERROR  Error generating route "/3424": This page could not be found                                                  23:42:28
20 ERROR  Error generating route "/3442": This page could not be found                                                  23:42:28
21 ERROR  Error generating route "/3584": This page could not be found                                                  23:42:28
22 ERROR  Error generating route "/3677": This page could not be found                                                  23:42:28
23 ERROR  Error generating route "/3548": This page could not be found

このようなエラーが出たのでpages直下に_test.vueファイルを作成すると

console
1ℹ Full static generation activated                                                                                    23:57:37
2ℹ Generating output directory: dist/                                                                                  23:57:37
3ℹ Generating pages with full static mode                                                                              23:57:37
4✔ Generated route "/posts/3642"                                                                                       23:57:37
5✔ Generated route "/posts/3600"                                                                                       23:57:37
6✔ Generated route "/posts/3610"                                                                                       23:57:37
7✔ Generated route "/posts/3584"                                                                                       23:57:37
8✔ Generated route "/posts/3424"                                                                                       23:57:37
9✔ Generated route "/posts"                                                                                            23:57:37
10✔ Generated route "/posts/3595"                                                                                       23:57:37
11✔ Generated route "/posts/3442"                                                                                       23:57:37
12✔ Generated route "/posts/3677"                                                                                       23:57:37
13✔ Generated route "/posts/3580"                                                                                       23:57:37
14✔ Generated route "/posts/3548"                                                                                       23:57:37
15✔ Generated route "/"                                                                                                 23:57:38
16✔ Generated route "/3642"                                                                                             23:57:38
17✔ Generated route "/3595"                                                                                             23:57:38
18✔ Generated route "/3600"                                                                                             23:57:38
19✔ Generated route "/3584"                                                                                             23:57:38
20✔ Generated route "/3442"                                                                                             23:57:38
21✔ Generated route "/3424"                                                                                             23:57:38
22✔ Generated route "/3610"                                                                                             23:57:38
23✔ Generated route "/3580"                                                                                             23:57:38
24✔ Generated route "/3677"                                                                                             23:57:38
25✔ Generated route "/3548"                                                                                             23:57:38
26✔ Client-side fallback created: 404.html                                                                              23:57:38
27✔ Static manifest generated                                                                                           23:57:38
28✨  Done in 17.94s.