Sure, people prepare! But that's a good thing. We want everyone to do well. If we sense they're doing something they've rehearsed a bit too much, we might push

Sure, people prepare! But that's a good thing. We want everyone to do well. If we sense they're doing something they've rehearsed a bit too much, we might push them to do it a bit differently. "What if you tried to do this by _____", just to make sure they can think on their feet. Honestly, though, the best candidates for us are the ones who wouldn't try to game it. They hear the prompt, and are just so excited to show and talk about a project they're building that it's not a problem!