SwiftUI sectioned list with large data set is sluggish - list

Question

I am trying to create a sections list of a large data set, 20,000 plus records, but this applies for even lower data sets of 5k records,
I have looked at
https://www.raywenderlich.com/27201015-dynamic-core-data-with-swiftui-tutorial-for-ios
and it works fine for a small data set of 20 records but once I add more data by editing this function to create more records
private func addTestFriends() {
let request = Friend.fetchRequest()
let context = PersistenceManager.shared.persistentContainer.viewContext
do {
if try context.count(for: request) == 0 {
for number in 1...1000 {
print(number)
try Friend.generateTestFriends(in: context)
}
}
} catch {
print("Error generating friends: \(error)")
}
}
Which results in 20,000 records the app is really really sluggish, just closing the sections with the disclosure is slow.
Is this a flaw in SwiftUI or is there a different approach?
I also looked at Apples
https://developer.apple.com/documentation/swiftui/loading_and_displaying_a_large_data_feed
which when doing a flat fetch of 10,000+ earth quakes loads fine, but once I try to section it
#SectionedFetchRequest(sectionIdentifier: \.code, sortDescriptors: [SortDescriptor(\.time, order: .reverse)], animation: .default)
private var quakes2: SectionedFetchResults<String, Quake>
sectioning it by "code" and it takes agessssss to load and then again is slugish
This seems a major flaw if you cannot create sections for large data sets of more that 1000 records