I said the same thing when they had blueberries on hand for the pre-heat. At the very least, I think they get hypotheticals, kind of like "if this were the task, what would you be most likely to do".
Weren't they all professional bakers? I'd expect a professional baker to know how to do a checkerboard cake. (I'd even expect that a home baker who applies for the show is well-versed and has a certain knowledge, otherwise, I don't think they should apply).
That could be how they edit it. (Although, I don't think that they just decide what to do on the spot either).