HotPlug is one of the turnkey versions of this, yes

Which is why if you want to defend against the easy versions of these and make people have to do work, only plug your desktop PCs into standalone outputs not on a surge protector.

Yes, it won't defend against cord cutting.

Edit: A more interesting defense I think would be to modify a surge protector for this specifically to defeat HotPlug. Only put your computer on a specific outlet and wire it so that if any other outlets complete circuit to kill power to the whole thing.