I'd say that it says saves at least half a second more than a ground pound jump. I'd say the drawback is perhaps it's inconsistency. It would take practice to master and if you mess up you long jump. It does move backwards but I'd say minimally especially if you're already holding forward. Definitely situational though. I'm sure there are only few times where this would come in handy.

Edit: Also in practice it's more of a high jump. Because you're holding forward the backward movement is really minimal. Qualitatively, the height seems about as high as a ground pound jump but I haven't quantified it really.

So normally when you run and press ZL+B, you long jump. However I was messing around and it turns out that, if you very quickly press AND release ZL, all of your momentum cancels and you enter the crouchstationary state. This is contrast to holding ZL where you enter a crouchslide state. The difference is that, in the crouchslide state, if you press B you long jump because you have momentum. But in the crouchstationary state, if you press B, you backflip (no momentum). This means that you can very quickly obtain the maximum height irrespective to your momentum by tapping ZL very quickly and pressing B.

Is this known? I'm probably not the first to find this but I'm curious enough to post it.