I certainly agree with you that the shape of the plate is the crucial factor, whether the crêpes are evenly cooked or not, but in science (pardon my virtuous expression) agreement does not amount to cogency. Experiment seems to me a more persuasive option.

Make another, extra-large batch of crêpes (try not to be distracted by sympathetically  imagining my wistful expression), share the products into two piles, one on that same plate, and the other on a flat surface (you might want to try  a third pile on a convex surface such as an inverted plate; after all, Rutherford got his first revealing breakthrough when he looked for scattering where he never expected to see anything!) and see what shapes you get. Such an extended experiment might not merely solve your problem, but leave you with new questions...