Cars also depend almost entirely on the road infrastructure. The automakers don't support that. People need to realise if they want interoperability they need to choose open standards that their community can maintain. This isn't just a problem with cars.
It's like calling a window a door. Yes, they are holes in walls that can be used for ingress or egress, but they completely different expected use cases and designs.
One could make the point that cars contain electronics with firmware which is so hopelessly broken that it needs constant updates. But the point in the article is even further from that and just that they are expected to interoperate with other things like remote services etc.
But like I said, the word is lost and people call iPhones computers too. I wish I hadn't written it now because it wasn't really my main point...
> What do people say now if they specifically mean a general-purpose computing machine?
"General-purpose computer" seems fine to me.
Newer cars are probably less likely due to how arbitrarily locked down they are, rather than being incapable. The manufacturer could run DOOM on their car that you bought, but you probably can't.