There is literally no legal distinction whatsoever between general-purpose devices and non-general-purpose devices. I don't know where this legal myth on HN came from, but there's no law anywhere saying Apple has to be one or the other, or that marketing has anything to do with what a device should be allowed or not allowed to do, nor does the law define these terms anywhere.

The part of the “general purpose computer” that Apple does not display in its iPhone marketing is the “computer” part including the original “there’s an app for that” commercial. Arguably also the “general purpose” part in that a general purpose computer will run any calculable task, and App Store + OS policies prevent this or at least make it difficult and the messaging around this also comes out of their crack marketing team. Feet to the fire, Apple would probably call iPhones pachinko machines before they ever called them general purpose computers in any part of their marketing.