In both survival and creative modes (I could only check one) when you are in the "Bow Sneaking" mode with and arrow pulled back, about half of the auto jumps that come when you walk up to a block are two early, and you have to let it jump a second time before you get up. It seems the difference speeds has the same way of auto jumping, but because one is much slower, it doesn't go far enough.

(Kindle Fire HD 7)