When the high nose forces the ball down into slate, it reduces the speed away from cushion but does not reduce the speed along the cushion as much, is one way to think about it. Cushion-ball collisions are very complicated. The ball loses up to 75% of its energy (50% of its speed) when hitting a cushion but the reflection angle is nearly ideal. That means that the cushion somehow reduces both directions of motion -- into and along the cushion -- about the same fraction.
When the nose of the cushion is nearer the equator of the ball, it pushes the ball away more efficiently and you get faster speed away from the cushion for a "shorter" bounce.
I used to play where the noses of the cushions were both low and sticky. Shooting the cue ball straight across the table it was possible to get six widths if you didn't launch the cue ball off the first one or two cushions.