Most out-of-round marbles would have come from the factory that way and weren't reconditioned. Probably different reasons for out-of-round. Before I start ad-libbing, I probably should ask if you have any particular marbles in mind. Antique German marbles would have different reasons for being out of round than modern Jabos would. I have been under the impression that machine-made marbles were more likely to be round during the age when kids were playing a lot of marbles, so I suppose that's where I'm most curious if you're thinking of examples there.
P.s., we lost Leroy in 2018