The deceiving logo marquee is the most annoying thing of this software era. "Popular with people that follow these companies on social media" is the next step to this madness.
Phosh is not based on gnome-shell and has its own settings and apps, but it does use parts of gnome, no reason to reinvent the wheel.
> Seems like a very strange bundle to bring in for an extremely power constrained device, where every % of increased battery drain is noticed by the user
I'm sure you can make your Frankenstein version that would be 10% as usable and secure as phosh by removing everything but for most users, 100mb more ram and 1% more battery drain for an OS aiming to be a daily driver is something that's worth it.