Cross-platform is a thing.
If anyting, Apple stands to gain from what was already developed for Android.
Like https://developer.android.com/phones-tablets-foldables
Which targets iOS also: https://kotlinlang.org/compose-multiplatform
It is a thing to some extent, but there’s also a correlation of companies that do cross-platform for simple apps being cheap on development, and making it work very well on some specific platform isn’t their priority.
React Native and Flutter are way more popular than KMM/CM, and yet both have struggled to support even small iOS visual changes in a timely fashion.
This is ignoring the fact that developers who choose these cross-platform frameworks don't seem to care much about quality and general polish.