What if:
You choose to use a mechanical advance-
BUT- supposeyou always jamb the throttle from low to full -as fast as possible. (not a great idea -but I see it all the time)
Doesn't the advance go to full even tho the engine is at say 2000 rpm?
As I recall - this really created a low/midrange shake.
On some engines - (heavy engine heavy/solid model -no problem).this would not be desireable.