How does preventing competition in a specific application category lead to Apple preventing Google from "forcing" iOS users to use Chrome? Not sure I follow your argument here or how allowing browsers would somehow make it possible for Google to automatically install Chrome for iOS users.

Imagine if Google suddenly made their Chrome browser behave differently on Google websites compared to others, like 0.5 the performance for no reason. This could be seen as a strategy to increase engagement on Google properties, but I'm fairly sure most of us would see it as an attempt on monopolizing the web in Google's favor. Why is it different for Apple and browsers? They are intentionally making it impossible to create competitors to their own browser, for no technological reason besides "we don't want that".