There has been an epidemic of problems, from what I have noticed, of either out of round or poorly finished aftermarket drums the last couple of years or so, especially the cheap ones from aftermarket suppliers like Advance, AutoZone, and O'Reilly. Many repair shops (not just chains, but independents and even dealers) deal with places like these, so it's likely your drums came from somewhere like this, especially if the emphasis was on cheap when you got it fixed. Depending on how obvious it is out of the box, I will often just turn them before installing them, just to prevent this sort of thing from happening.
Another possibility is that there is a buildup of rust and scale on the hub where the drum seats onto the car. This can cause the appearance of the drum being out of round by not allowing it to seat properly. That could be why it took two visits to clear it up, barring the possibility that the technician doing the work did not use the lathe properly the first time. If it's not giving you problems now, though, just don't worry about it.