Originally Posted by
chaadster
I still do not agree with that, though as I said, it may do as much with setup as biomechanics, but it's certainly not true for me, and I've spent plenty of hours just staring at power numbers to know it empirically. Furthermore, I've ridden hills steep enough that sliding back would fairly land you on your back; when the front has to stay weighted, you've got to shift your weight forward.
Two different concepts. You slide back on the seat to engage your glutes and hamstrings more.
You may need to move your weight forward to keep the front weighted on a steep climb, but you can do that by bending your elbows and moving your upper body down and forward.
Entirely possible to slide to the back of the seat to engage different muscles, and still keep weight on the front wheel.