When I first started watching this show years ago, I'd wonder how they'd decide who gets to go through to the actual show from the auditions. I would imagine it's tough, early on, for the judges to decide if someone did, or didn't, deserve to be in the top-20 having only tasted a few dishes and not having much to compare it too. How silly would it be should someone cook in an early matchup, have a great, but not better than the person next to them, dish... only to be denied a spot, and have everyone that follows fail to measure up and be sent home prematurely?
Then I realized that they must have some idea of who is going to be a talented chef, and who is cannon fodder, before the judges actually taste their food.
I mean, if the producers are watching audition tapes, then call up a cook to say "we're thinking of having you audition, what's your signature dish?" and he says "I'm going to mix a traditional Indian stew from my homeland into a classic Creole delicacy of my adopted country," and you just know they penciled him in as one of the 20 'contenders' to make the cut.
Then they just had to find 20 other idiots to round out the rest of the competition to make it good for TV. And they knew they had one of them all set when he answered the signature dish question with: "I'm going to bake a vannoli. It's a vagina cannoli."