GNUのcsplitとBSDのcsplitは挙動が違う？

Question

csplitの挙動がGNUとBSDでかなり違うようなのですが、POSIX的にはどちらが正しいのでしょうか？
（サンプルは 逆引きUNIXコマンド/指定したキーワードでファイルを分割する・csplit より拝借しました）

GNU版

user@demo:~$ cat denpyo.txt 
PRODUCT NO: 1
PRODUCT NAME: SQL SOFTWARE
PRODUCT PRICE: 100
PRODUCT NO: 2
PRODUCT NAME: OS SOFTWARE
PRODUCT PRICE: 200
PRODUCT NO: 3
PRODUCT NAME: HTML SOFTWARE
PRODUCT PRICE 300
PRODUCT NO: 4
PRODUCT NAME: NETWORK SOFTWARE
PRODUCT PRICE 400
user@demo:~$ csplit -f denpyo/ denpyo.txt '/^PRODUCT NO:.*/' {2}
0
60
59
123
user@demo:~$ ls denpyo/
00  01  02  03
user@demo:~$ cat denpyo/00
user@demo:~$ cat denpyo/01
PRODUCT NO: 1
PRODUCT NAME: SQL SOFTWARE
PRODUCT PRICE: 100
user@demo:~$ cat denpyo/02
PRODUCT NO: 2
PRODUCT NAME: OS SOFTWARE
PRODUCT PRICE: 200
user@demo:~$ cat denpyo/03
PRODUCT NO: 3
PRODUCT NAME: HTML SOFTWARE
PRODUCT PRICE 300
PRODUCT NO: 4
PRODUCT NAME: NETWORK SOFTWARE
PRODUCT PRICE 400

BSD版

PRODUCT NO: 1
PRODUCT NAME: SQL SOFTWARE
PRODUCT PRICE: 100
PRODUCT NO: 2
PRODUCT NAME: OS SOFTWARE
PRODUCT PRICE: 200
PRODUCT NO: 3
PRODUCT NAME: HTML SOFTWARE
PRODUCT PRICE 300
PRODUCT NO: 4
PRODUCT NAME: NETWORK SOFTWARE
PRODUCT PRICE 400
mmns2016:~/projects/playground/csplit $ csplit -f denpyo/ denpyo.txt '/^PRODUCT NO:.*/' {2}
60
59
60
63
mmns2016:~/projects/playground/csplit $ ls denpyo/
00 01 02 03
mmns2016:~/projects/playground/csplit $ cat denpyo/00 
PRODUCT NO: 1
PRODUCT NAME: SQL SOFTWARE
PRODUCT PRICE: 100
mmns2016:~/projects/playground/csplit $ cat denpyo/01
PRODUCT NO: 2
PRODUCT NAME: OS SOFTWARE
PRODUCT PRICE: 200
mmns2016:~/projects/playground/csplit $ cat denpyo/02
PRODUCT NO: 3
PRODUCT NAME: HTML SOFTWARE
PRODUCT PRICE 300
mmns2016:~/projects/playground/csplit $ cat denpyo/03
PRODUCT NO: 4
PRODUCT NAME: NETWORK SOFTWARE
PRODUCT PRICE 400

Answer 1

BSDとPosixとGnuのman、Gnuのinfoを見比べると、オプションはBSDとPOSIXが同じですが、記述の文章自体は、

Gnu (Linuxにてinfo csplit)

Create an output file containing the current line up to (but not including) the next line of the input file that contains a match for REGEXP.

POSIX (Linuxにてman 1p csplit)

A file shall be created using the content of the lines from the current line up to, but not including, the line that results from the evaluation of the regular expression with offset, if any, applied.

BSD (FreeBSD 12のman csplit)

Create a file containing the input from the current line to (but not including) the next line matching the given basic regular expression. An optional offset from the line that matched may be specified.

で、同じ意味のことを書いてあり、他の部分の記述を見ても、man infoだけからは判断が難しいです。POSIXのより詳しいドキュメントか、ソースを見ないと。
「オプションの書式が同じなのでBSD仕様がPOSIX仕様では？」という推測は出来ます。

BSDでは「カレント行」の初期値が1行目で、Gnuでは「カレント行」の初期値が0行目ということなのでしょう。初期値が0行目というのはやや無理がある気がしますが。

Answer 2

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/csplit.html

見た感じBSD版のほうが正しそうに見えますね。