That's not uncommon, actually. Back in the day, shows got ground to match the radius/diameter of the drum. Can you say asbestos dust? No one does it these days and QC on brake shoes is Garbage at best unless they're actual OEM parts for a late model (and few of them use shoes anymore).
Just keep adjusting them as they wear in. Or try to find an old school brake guy who still grinds shoes. Better yet, go to rear disc brakes and enjoy a simpler life
