If the viberation is coming from something not right in the drive train, then not only would you only really notice it while moving, I would suspect that the seat would not be the only place you would feel it, most likely in the bars and foot rests as well.
Too bad the seat was reworked instead of switched, that way you could switch back and see if the amount of vibration you notice in it changes. Maybe the removal of some foam or density of the foam they used accentuates what you are feeling.
