It's not really though, regardless of it's graphical prowess, the purpose of an engine is be able to ship a game, which means fast iteration times, effective pipelines etc. Unity is great at that, but if the developers feel that they can create a card game the best and the fastest with UE4 (which wouldn't be a stretch, since BP can be very effective at rapid iteration cycles), I don't think there's really anything to laugh about.
I can't speak for consoles, but none of the UE4 PC games I've played so far exhibited any of the intermittent stuttering issues which commonly plague Unity games.