Not a valid comparison. An automotive entertainment system is not a general purpose computing platform.
That is a farcical separation. There is no such thing as general purpose computing.
By your reasoning game consoles and cars are specific purpose computing devices, but:
- Game consoles can stream video and have web browsers (office online anyone?).
- Car infotainment systems allow for installable or non-car-specific applications. A Tesla can even run Netflix or video games so you can be entertained while charging.
By the same reasoning a phone is specific purpose device. It is primarily defined to be a PHONE. The fact it has evolved to also run other apps does not negate the fact it is a PHONE. (or, "a PHONE. an IPOD, an INTERNET COMMUNICATOR. Are you getting it yet?" -SJ 2007)
The fact is that all of these devices - PC, Mac, iPhone, iPad, Xbox, PS5, TVs - are COMPUTING DEVICES as they have a CPU, RAM, Storage, and an OS. Some are more locked down that others for various reasons, but they are all essentially computing devices.
Locking the car down for vehicular safety makes sense. Locking a phone (iOS or Android) down for general user protection makes sense. There are an order of magnitude more iPhones, iPod touch, iPad, Android phone and tablets than there are Macs. So equating the use cases and user base of phone vs Macs is not a clear parallel. The number of devices in the wild; the profile of user; the type of data available to a bad actor is significantly more voluminous and sensitive than what many users have on the Macs or PCs. And phones are always with us and always on. Again, unlike most PCs and Macs.
Edit: All that said, I would like to see the iPad Pro M1 open up a bit. It could support some level of additional capability. But I would still expect App Store and/or signed apps only. No wide open installation. But I would also expect that to be a forked "Pro" version of iPad OS or MacOS on iPad.