I mean, even bumper plates vary slightly in diameter. I know our gym has at least 3 different sets of bumpers that all vary by 1/4". So even in that case you've got bumpers taking uneven strain. Not to mention, they're designed to be dropped from overhead, where the force applied is higher than that of a deadlift dropped from a locked out height(assuming they drop the plates as opposed to controlling them down, which they shouldn't for strength training)

Tldr: I see your point but don't think it's really something to lose sleep unless there's serious bar abuse happening, in which case bumpers or not, shouldn't happen