Can you explain this claim? It seems very clearly false to me, so perhaps we're thinking about things in very different terms here. To me, the extremely obvious and fundamental difference between the two is that we have a very good explanation (to use Deutsch's favorite term for emphasis, although that terminology isn't strictly important here) for why we know the probabilities of various events in a game of cards. Of course, our explanation of why we know those probabilities does depend on some assumptions of our model, namely some things about how the cards are shuffled and dealt, but the explanation doesn't really have anything to do with modeling subjective uncertainty of a particular observer. Sure, it is probably physically possible for some observer to have more certainty, like someone just outside the room with an extremely sensitive radar, but that observer would likely be understood to be violating the rules of the game (just like any card player who cheats using more feasible methods).
To me, that's fundamentally different from invoking probability when discussing things like the existence of a specific thing in a specific unexplored part of the world, again assuming we don't have some explanation for why the existence of that thing in that place actually has a probability associated with it.