Well no it isn't Rob; if both stock and 3rd party PSUs turn it 0.02% WRMS or suchlike, then clearly it doesn't explain why one sounds better (or more rhythmically correct) than the other!

It's also important to point out that such measurements don't account for dynamic wow, and how the motor responds to short-term demands. This is likely to have just as much effect as vibration pathways, and is constantly overlooked. Would you assess a car solely by simply driving it at 56MPH and assessing how easily it stays at that speed?