I do this, too -- I'm in the same seated/tucked position, but my weight is almost all on my feet, cushioning potholes and it at least feels to me like I have more control, not less. I don't do it to give my butt a break -- I have a pretty tolerant hind end -- I do it to be able to move my weight around to handle terrible road surfaces. Or at night, when I have to just assume the road is going to be a horrorshow and I'm not going to see crap until it's almost under my wheels.