[Bug] Aspect settings not working on MacOS (4.3-pre)

Description

Only 1 of the 3 aspect settings works on XF Mac.

Steps to Reproduce

1. Create a Xamarin Forms project from template
2. Add the Mac project to it as per document: https://docs.microsoft.com/en-us/xamarin/xamarin-forms/platform/other/mac
3. Add image controls to the main page with each aspect setting being used.
4. Run the app.

Expected Behavior

The expected behavior is demonstrated on iOS:

Actual Behavior

The actual behavior in a MacOS window:

Basic Information

• Version with issue: 4.3-pre3
• Last known good version: ?, but this appears to be a recent major refactor that would be my guess at when it broke: https://github.com/xamarin/Xamarin.Forms/commit/ce148bf4c81f7d1da5ef74c7a2a43cca6ca73331#diff-59032a35e10fb51bc88a456719271ac1R1-R12. I think it may have lost some things (see my comment at the end of that link).
• IDE: VS on Mac

Reproduction Link

ImageAspect.zip