The difference is a phone has never been a general purpose computing device. So saying that we need to make them one so that laptops remain one sounds to me akin to “if we don’t have full control of the software our watches run, we might one day end up not having full control of the software our laptops run”. It’s a bizarre comparison to make in my opinion.
I think you have it backwards. A general purpose computing device had never been a phone until recently. Now that it is, why should it have to lose its general purpose computing roots.
I dreamed about having a portable computer, somewhat like what my phone is now, when I was a kid. It ended up even cooler than I imagined it. The eventual device that came along has amazing battery life, oodles of CPU, RAM, and secondary storage, a wide array of sensors, multiple cameras with high resolution sensors and great optics, water resistance, exceptional build quality, a very small form factor, and it's at a price point that's reasonable. It's all great, except that I don't actually own it and can't use it for what I want.
Giving up control of the devices we own is dangerous. It most certainly is a slippery slope. The manufacturers will use "security" and "privacy" as a way to erect walled gardens on our heretofore general purpose computing devices. They will use the walled gardens to extract more revenue from developers and end users, and they'll act as police over what are "acceptable" applications. The average non-technical person doesn't understand why it's a problem, and those of us who are technical should be championing ownership instead of giving up control.
Chromebooks had a physical interlock that enabled/disabled the "trusted" functionality (perhaps they still do-- I haven't followed them). That is an acceptable solution, to me. It wouldn't be difficult to do, either. The fact that manufacturers don't include such functionality speaks volumes about their motivations.
If it is designed to run arbitrary software, clearly it's a general-purpose computing device, no? And maybe the ergonomics of phones makes their potential as general-purpose computers limited, but that argument doesn't fly for tablets (even on HN people use their tablet as a main work device, eg: https://news.ycombinator.com/item?id=22731192), and iirc Apple's draconic policies also extend to iPads.
It certainly looks like a slippery slope from where I'm standing. People have gotten used to not having full ownership of their phones, and tablets are kinda just big phones, so people have gotten used to not having full ownership of their tablets. But a tablet is also kind of like a small, highly portable laptop, and in fact many people use them as such. The boundary between the two is also blurring, with tablets becoming more laptop-like and laptops becoming more tablet-like.
I don't think it's a huge leap from here to fear that we are witnessing a trend, and that our ownership of our true general-purpose computing devices, such as our laptops, is not something we should take for granted.
