Elementary question for stick cars

[older racer]

ok, I use to wait till top bulb came on then matted throttle, the car seemed to bog some through first gear. I was told to matt it before tree came down, this would clean out the extra fuel in manifold make for a cleaner launch, I tried it, picked up .02 in sixty foot, worth .04 at end of track. no more bogging ! just something to consider.