Software repositories can distribute whatever software they want, the examples you've given are of arbitrary decisions made by repo owners. Furthermore, Win32 isn't an 'ecosystem', it's just a set of APIs you can target to pantomime software behavior. It doesn't relate to software distribution whatsoever, just as the Darwin/XNU kernel doesn't handle packaging.

In fact, you've done a very good job of highlighting the problem with the iPhone. MacOS' software distribution works because it offers a distribution-agnostic API for native apps, same as Windows. iOS/iPadOS don't expose those interfaces to the user, which means the only way to 'install' an app is with Apple's good graces. Compared to Debian, where you can still install non-free packages regardless of how it exists in the repo, Apple's status quo is considerably more restrictive (and abusive).