I am well aware of what AOSP stands for, but what you say doesn’t really make sense. OneUI, MIUI, etc are all derivatives of Google’s Android i.e. all come with Google Play Services installed as a system app. So, however you might frame it, it is still in fact a sensible thing to use the term “Android” to refer to “Stock Android” with Google when talking about these topics. Moreover, this is also very useful to make it clear to people who are not aware of the intricacies of AOSP how some operating systems DO NOT depend on Google services. You can see this being used by companies like Tutanota on how to “Degoogle your life”. The simply put, as a replacement for Android, CalyxOS, /e/OS, LineageOS, etc. Despite these being AOSP based ROMs, using Android to refer to google based systems and AOSP to refer to independent ROMs that do not come with Google Play Services by default is VERY useful to make the point come accross. If you don’t believe me, look at any popular news media source that talks about GrapheneOS, for example.

PD: I still believe the fact that Android is a patented trademark of Google gives validity to the expression, regardless of how one might feel about patent law.