well for getting maximum phat air off jumpy descents!
For one thing… and also Trail Centres tend to be designed with a bunch of different features on one run (undulating sections, jumps, drops, all sorts of stuff, right?) so it is a real bonus (to me anyway) to be able to just drop my saddle whenever I spot something up ahead that would benefit from it… Brechfa is a good example I think…
And yes
getting your weight lower centrally over the bike helps quite a bit in lots of situations.
I find this is the case as well! Again, a GD really shines in this situation, you hit the bottom of the descent, click with your thumb, and your saddle is back up at optimum climbing height for the hill in front of you, no need to stop… superb 8)