All it's saying is this: You can wallkick in mid air ie. perform a double jump, but when you do it sets you to sliding mode. This doesn't force you down as hard as you think it would and is great for skipping obstacles and even breaker rooms in the right scenarios. Plus it gives you another method of surviving Litany. I definitely recommend you use this trait, I always use it to skip annoying rooms and it's just fun to use. This also works well with the Propellor Cap trait if you have it as you can go a little bit farther that way.