Think of it just the same as a tac(albeit with a lot less bend), you aren't running at the wall and kicking the crap of it, you are placing your foot on the wall, bending a bit and then powering out of it. Same kind of thing, nice low hurdle into your punch, land it almost like a precision then power up/out with it into your vault/flip.
That's how I think of it at least, especially on harder surfaces, it's not nearly as important on a spring floor or spring board, in fact that might keep you from utilizing all the power you can from the floor or board. Not too sure about the floor but for sure on a board you want to hit it as hard as you can generally.