Yeah, it's fucking stupid and awful.
But it also seems like it goes against Sony's policy of "if you buy anything discounted with PS+, you keep it when you unsubscribe from PS+". So I'll be really surprised if they don't change their stance on this Driveclub fiasco. Unless they are changing their stance in general and PS4 games will screw you over if you buy them on PS+ and don't keep PS+.
Actually reading more about it, it seems like it's screwing up because it's counting it as DLC and not an actual game. And if you buy DLC for a game that you got for free on PS+ and you unsubscribe, the DLC doesn't work because you don't have the game to boot into it, which is what's going on here.
What Sony should do because this is really bad PR, is change it so it's not an "upgrade DLC" from the free PS+ version, but simply that if you own the PS+ version you get a $10 discount from buying the retail "game" on the PSN store. That would fix this and people would still keep the game when they unsubscribe. They're not changing their original policy, they just screwed up by marking this as a DLC upgrade instead of a retail game.