Do platform holders have a say in this?

I'm sure if I submitted an app that on the iOS app store that mimicked a system warning that tried to scare people into giving me access, it would not pass the review process.

If instead I decided to embed a WebView and later changed the html to do the same I would likely get booted from the app store (afair Apple's very particular about serving remote content in PWAs, and changing said content, even under benign circumstances).

iOS seems to have less scareware and shady apps than Android anyways.

the app store is filled with scammy apps, its just a different flavour

I once got a crypto-wallet PK leaked by a fake wallet app impersonating another very known brand. Found out on reddit it was a fake... After a few months the real app came out but yeah...