The only time I ever seat bounce a jump is if it is so close to the turn before it that I don't have enough room to get the speed to clear it normally. Therefore, I only do it in 2nd, maybe 3rd gear with a fairly short run.
If I have time to hit 4th or 5th gear, I've got more than enough room to accelerate and jump it from a safer and more normal position.
Seat jumping (for me) always tends to make the rear rebound more than the front and, while it does throw the whole bike higher, it throughs the rear up more than the front. Doing something like that at the speeds of 4th or 5th gear sounds downright scarey to me.
P.S. What fresnosmooth described did not sound at all like seat bouncing a jump to me.