Allegedly, yes. But the person who has seen it before is able to arrive at an answer, have it be ideal, and justify it, a lot more readily than someone who has never seen it before. That's what the OP was even saying; if he's seen it before he does fine, if he hasn't he struggles and freezes up. That describes a LOT of people. It's also why I tend to interview with trivial questions, things that algorithmically have no trick at all to them (or we give them the algorithm).