ABS grabs and releases the breaks rapidly, so there is no reason why i can't or shouldn't perform the same action to achieve the same goal.
Going down really steep hills in SF, I can decrease my stopping distance by alternating pressure on front and rear brakes, in turn, and rapidly. The pressure and release are still progressive in that I am always breaking with both front and rear just more with one than more with the other. its not full on full off, that would give you (as stated) an undesirable amount of weight transfer back and fourth.
if I were to break down the entire hill without giving the pads a rest, they would become too hot to work efficiently by the time I got to the bottom.
Yeah, I probably need new pads as I've never been at risk of locking up my breaks, but they do fade with heat, and "pumping" them helps to remedy this.