Oftentimes, a toss forward can shorten reply time, but not hit faster or make the ball bounce higher.
Can we agree a backspin serve bounces lower than a topspin serve?
Tossing too far forwards often encourages a backspin serve when trying to hit really hard.
Tossing just in front of the baseline can often account for a serve that his hit with a slight forward spin, not a topspin serve per se, but a flat serve with a dead ball effect. Those seem to go the fastest and really bounce high.
I know this is counter to what lots of you have noticed, but I've talked to guys with big serves, and they all say that going to net often compromises their bounce and pace.