Grouped CollectionView lazy loading does not trigger [RemainingItemsThresholdReached] on iOS and Windows

[hbraasch]

Description

When populating a CollectionView with grouped data, the [RemainingItemsThresholdReached] event does not trigger for iOS and Windows when the [RemainingItemsThreshold] value is reached.

This works fine under Android.

A simple repro is provided.

See here how Android works (must admit, it throws a low-level exception each time the threshold is reached, but maybe that is by design)

https://user-images.githubusercontent.com/7484186/189766047-067038e0-0c7d-4184-b3c1-3944c2ed3eac.mp4

See here how iOS only loads the first chunk, then never triggers when scrolled down.

https://user-images.githubusercontent.com/7484186/189766117-98eec0a2-c54b-4a45-b5f6-8da9cf036158.mp4

See here how Windows loads the first chunk, then never triggers when scrolled down.

https://user-images.githubusercontent.com/7484186/189766169-101b873b-9c7d-4b7a-bdaf-f9dbb359f684.mp4

Steps to Reproduce

1. Load the project in VS from the Github repro
2. Run the app for the three projects
3. The applicable code is in file [StartupPage.cs]

Link to public reproduction project repository

https://github.com/hbraasch/ChunkTester.git

Version with bug

6.0.400

Last version that worked well

Unknown/Other

Affected platforms

iOS, Windows

Affected platform versions

Android 12 - API 31, windows10.0.19041.0

Did you find any workaround?

No

Relevant log output

No response