swiftUIにてfetchRequestにてTabviewの内容を正確に表示させたい

Question

前提・実現したいこと

swiftUIにてfetchRequestにてTabviewの内容を正確に表示させたいです。

ここに質問の内容を詳しく書いてください。

https://www.hackingwithswift.com/books/ios-swiftui/dynamically-filtering-fetchrequest-with-swiftui

https://www.hackingwithswift.com/quick-start/swiftui/how-to-create-scrolling-pages-of-content-using-tabviewstyle

上記２サイトを参考にした所、List表示では問題なく動作しますが
Tabview表示にすると正常動作しません。
（Tabviewの横スライドが最後までできません）

発生している問題・エラーメッセージ

特にエラーメッセージは発生していませんが、挙動がおかしいです。
ForEach文のMAX値が必要なのかもしれませんが、どのように適用すればよいのか、わかりません。

ご指導、よろしくお願いします。

import SwiftUI
import CoreData

struct ContentView: View {
    
    @Environment(.managedObjectContext) var moc
    @State private var lastNameFilter = "A"
    
    var body: some View {
        VStack{
            
            FilteredList(filter: lastNameFilter)
            
            Button("Add Examples") {
                
                let taylor = Singer(context: self.moc)
                taylor.firstName = "Taylor"
                taylor.lastName = "Swift"

                let ed = Singer(context: self.moc)
                ed.firstName = "Ed"
                ed.lastName = "Sheeran"

                let adele = Singer(context: self.moc)
                adele.firstName = "Adele"
                adele.lastName = "Adkins"
                
                try? self.moc.save()
            }

            Button("Show A") {
                self.lastNameFilter = "A"
            }

            Button("Show S") {
                self.lastNameFilter = "S"
            }
            
        }
    }
}

struct FilteredList: View {
    
    var fetchRequest : FetchRequest<Singer>
    @Environment(.managedObjectContext) var context
    var result: FetchedResults<Singer> { fetchRequest.wrappedValue }
    
    var body: some View {
        TabView{
        //List {
            ForEach(fetchRequest.wrappedValue, id: .self) { singer in
                Text("(singer.wrappedFirstName)(singer.wrappedLastName) ")
            }.onDelete(perform: deleteitems)
        }
        
        .tabViewStyle(PageTabViewStyle())
        .indexViewStyle(PageIndexViewStyle(backgroundDisplayMode: .always))
        .background(Color .orange)
        
    }
    
    init(filter: String) {
        fetchRequest = FetchRequest<Singer>(entity: Singer.entity(), sortDescriptors: [], predicate: NSPredicate(format: "lastName BEGINSWITH %@", filter))
    }
    
    private func deleteitems(offsets: IndexSet){
        offsets.map { fetchRequest.wrappedValue[$0] }.forEach(context.delete)
        try! context.save()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
import SwiftUI
import CoreData

struct ContentView: View {
    
    @Environment(.managedObjectContext) var moc
    @State private var lastNameFilter = "A"
    
    var body: some View {
        VStack{
            
            FilteredList(filter: lastNameFilter)
            
            Button("Add Examples") {
                
                let taylor = Singer(context: self.moc)
                taylor.firstName = "Taylor"
                taylor.lastName = "Swift"

                let ed = Singer(context: self.moc)
                ed.firstName = "Ed"
                ed.lastName = "Sheeran"

                let adele = Singer(context: self.moc)
                adele.firstName = "Adele"
                adele.lastName = "Adkins"
                
                try? self.moc.save()
            }

            Button("Show A") {
                self.lastNameFilter = "A"
            }

            Button("Show S") {
                self.lastNameFilter = "S"
            }
            
        }
    }
}

struct FilteredList: View {
    
    var fetchRequest : FetchRequest<Singer>
    @Environment(.managedObjectContext) var context
    var result: FetchedResults<Singer> { fetchRequest.wrappedValue }
    
    var body: some View {
        TabView{
        //List {
            ForEach(fetchRequest.wrappedValue, id: .self) { singer in
                Text("(singer.wrappedFirstName)(singer.wrappedLastName) ")
            }.onDelete(perform: deleteitems)
        }
        
        .tabViewStyle(PageTabViewStyle())
        .indexViewStyle(PageIndexViewStyle(backgroundDisplayMode: .always))
        .background(Color .orange)
        
    }
    
    init(filter: String) {
        fetchRequest = FetchRequest<Singer>(entity: Singer.entity(), sortDescriptors: [], predicate: NSPredicate(format: "lastName BEGINSWITH %@", filter))
    }
    
    private func deleteitems(offsets: IndexSet){
        offsets.map { fetchRequest.wrappedValue[$0] }.forEach(context.delete)
        try! context.save()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

import Foundation
import CoreData

extension Singer {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Singer> {
        return NSFetchRequest<Singer>(entityName: "Singer")
    }

    @NSManaged public var firstName: String?
    @NSManaged public var lastName: String?
    
    var wrappedFirstName: String {
        firstName ?? "Unknown"
    }

    var wrappedLastName: String {
        lastName ?? "Unknown"
    }

}

extension Singer : Identifiable {

}

import Foundation
import CoreData

@objc(Singer)
public class Singer: NSManagedObject {

}

試したこと

AppleフォーラムやStack Overflowを調べましたが
Tabviewのバグ？という意見もあります。

補足情報（FW/ツールのバージョンなど）

XCODE Version 12.1
IOS14.1

ここにより詳細な情報を記載してください。