I put together the most extreme half swap I could… half Dread G (80g version), half Smashing Crucible (50g). Massive difference in shape, diameter, and weight, see for yourself 
Again… dead smooth on the string. It does list heavily to the side and it wants to turn because of the weight differential, but it’s perfectly vibe free. Seriously. I wouldn’t have believed it myself if I hadn’t tried it!
I’m starting to wonder if the halves matter less than the internal symmetry on each side, that is, distort the weight distribution of any side and that’s the origin of vibe. Because clearly mismatched sides isn’t causing vibe!
(Also agreed that this shows the alignment of the bearing and bearing seats and axle is extremely important.)