This is how I see it: As it is necessary to install a spacer, on the axle, between the inner races of the two bearings, so that the snap ring on the bearing's outer race does not actually preload against the hub, there's no firm reason to have the tube perfectly cut on the ends. Sure, it would be nice, but I'm thinking nobody is going to get a set of feeler gauges and check the gap between the snap ring and the hub all the way around.