My understand is Astral's focus for ty has been on making a good experience for common issues, whereas they plan for very high compliance but difficult or rare edge cases aren't are prioritized.

Compliance suite numbers are biased towards edge cases and not the common path because that's where a lot of the tests need to be added.

My advise is to see how each type checker runs against your own codebase and if the output/performance is something you are happy with.