So then most smartphones should be considered a PC then.
See - it's a slippery slope.
Actually, yes. Most smartphones are PCs.
I don't think this is a slipperly slope at all. The reason to define things is to understand what we're talking about. If we insist on defining things by arbitrary things like input methods or whether you can download stuff from a particular website then we end up only adding to confusion.
A thing is a PC if it is used as a PC is used. It doesn't matter what shape it is, what colour or what it is made of. If you took the guts out of a normal desktop PC and built them into the frame of a sofa and interacted with it by jumping up and down on big peddles it would still be a PC. An odd sort of PC but a PC none the less.