I already have two secure conclaves in my phone, and they're already used up for other apps, e.g. finance apps, etc. One of them uses Work Profile and the other uses Knox. I don't think that more such regions are allowed on non-rooted Android.

As for iOS, to my knowledge it doesn't allow for any such app segregation.

In general, we need stronger per-app isolation such that a zero-day affecting one app doesn't grant any access to anything else.