This is going to cripple them in the market. Removing features does nothing to make a vehicle more attractive to the average idiot. Maybe GM thinks they can get away with it because the demand for cars exceeds the supply right now, I don't know.
They see how much money Google and Apple are making selling your data and want a bigger cut so they need to make it so they're the only source of data extraction then your data is more valuable.
This isn't much different than smart TVs pushing their shitty outdated apps on you versus using something like a Roku or Firestick which is third party and updated regularly. This is a classic GM move of taking the exact wrong action on something and expecting great results. This is why they keep going bankrupt.
I have an older Roku tv. I recently got a nice roku streambar and hooked it up to the older Roku tv.
The tv displayed a popup with a message along the lines of “Oh hey, we see you connected a newer Roku device. No worries. Well just use it instead of the older built in one and you’ll never know the difference.”
As they mention in the article, tesla and rivian are doing quite well and both have opted not to integrate with phone mirroring options. So it's a gamble, but they may think they can get away with it. Like you say, the high demand may be giving them the confidence to try.
Tesla and Rivian are both newer electric-only manufacturers, though (unless there's something I don't know about Rivian). Their market is quite different from stodgy old GM's.
And their software integrated into their cars is much better and receives OTAs (as a Rivian owner). However also as a Rivian owner: I'd prefer car play/AA.
They're probably still marketing to boomers, maybe an ok play in the short term, but that target audience is probably not going to prop them up forever