My hot take is that this is largely a product of how many guitars are bought sight unseen over the internets these days. In the olden days you bought a guitar after you felt it up. Nowadays people plunk down thousands of dollars on a guitar they've never handled and want some assurance of how it'll feel. But, yeah, "C" covers a lot of subjective territory. Ricky above describes his Epi "slim taper" neck as a fat C. If it's the same slim taper as my '61 reissue Casino, I'd call that a D, because it's wider than it is round. If that even makes sense.