"Sit up" doesn't mean "bounce high." It means "bounce straight up." Usually it's underspin shots that sit up. And yes, when they do that they bounce higher than normal. Which I suppose is why sloppy thinking got "sit up" confused with "bounce high."First of all, forget the "topspin serve. All that a topspin serve does is cross the net slower than a flat serve and sit up nice and high so that it is easier to pound away for an agressie return. There is really no advantage to a topspin serve and several dis advantages. The disadvantages are-- it is more difficult to hit, harder on the back and arm/wrist.
Ust the kick serve for doubles or a second serve in singles.
There are many threads on this, even within the last few days. Look them up or do a search.