> it’s also quite convenient for Apple that all this stuff is effectively non-replaceable / upgradable

On the other hand, I’m happily banging away on my ca. 2020 M1 MacBook Pro. It just got a warranty service, free to me, that replaced the screen. It will probably get replaced around 2030. That simply isn’t the norm with the alternatives.

The hypothesis that this is self serving isn’t supported by the evidence. Instead it’s more parsimonious to conclude that this is Apple being Apple with pushing design to the limit when it comes to executing a vision. User-upgradable parts have not been part of that vision since Jobs returned.