Re: Scratching my head
Vendor customisation is not the issue. As you point out, the hardware isn't standard, and specific hardware needs specific software, which has to be compiled especially for the hardware.
So, it's the drivers and stuff that are the reason updates are exclusive to the phone - if that wasn't the case, you could simply update over any vendor customisation such as wallpapers, launchers, installed apps, 'settings' interface/functionality etc.
Google supposedly remedied this - from the release of Android Orio onwards, all hardware designs are meant to decouple the drivers and low level firmware etc. from the upper level android OS. Basically, this means that whilst the hardware may be non-standard, the hardware interface that android sees is unified. Hence, all such devices should work with the generic OS updates/patches.
That's the theory . It's called "Project Treble" (https://android-developers.googleblog.com/2019/10/all-about-updates-more-treble.html, but I've yet to see it work in practice!
Biting the hand that feeds IT
