I call those Android flavours. Those are not separate OSes. Windows Mobile was a third mobile OS. /e/ OS is not.
Just like there are not tens of different browsers out there: all the Chromium-based are essentially Chrome with small changes (that people care about, but still small changes).
- a SMS app - a Maps app or API - a location API - a web browser - an alarm app - Remote notification system - app store (and there are many many other examples)
can be called a smartphone OS. Yet AOSP doesn't contain (Google/)Android version of those.
So yes, I dare say AOSP-based OS can be non-Android.
No offense, but you should re-think your definition of "OS"