wbm: The "logic flow relates to someone that wouldn't bother to clean their brass. Stuffing dirty brass in your action would be the last thing I would be doing. And if they couldn't be bothered to clean their brass, I would wonder how well they take care of the rest of their gear?
When someone mentions using a "tumbler", the first thing that comes to mind (to me at least) is they're talking about cleaning their brass.
If you clean your brass by wiping it down, it's the "exterior cleaning" that you're concerned with. At least you're going to the trouble to get the grit off.
After a good range session, the last thing I want to do is wipe down 300+ .308 cases from my M1A, one at a time, by hand. My BR brass never hits the ground. Single feed, extract , inspect and back in the box.
I like clean brass that gets a close inspection, each and every time.
If you don't use a tumbler, at least you're cleaning your brass.