In days of old,, we had a "brake shoe arcing machine", that'd grind on the shoe till it matched the arc of the drums, cuz it changes as the drum wears, or is machined.. That was asbestos dust being ground off, and became frowned upon cuz of health reasons,, so no more matching shoes to drums.. You just wear em in now.. by driving..
So depending on your drum size,, it's common to find the shoes either touch on the leading/trailing edge,, or ,, a few inches right in the middle..
hope it helps
P.S. The shoes will seat faster, if the drums have been machined..