Answer 1

bit of a clarification, you don't get any more speed than you already have while falling. It's just that hitting knight shields while falling doesn't reset your fall speed like many other things in the game do, so I guess optically it looks like a boost.

Answer 2

So you're actually building downwards speed while being kinda frozen in the air and attacking the shield?

Answer 3

well no, you don't build any speed at all, per se. you just don't lose any.