The bhop bonus is broken. You have each bhop as 128 units below the last one. When you bhop (bouncehop), you're jumping on the pseudo-ground, not the ground. Pseudo-ground is 0-2 units above the ground. This means that when you bhop, you gain a small amount of height. After 2 bhops, you've gained enough height where the 129 unit height no longer works.
In order to complete the bonus, you have to edgebug, since it's not possible to bouncehop from the third set onwards. We've already managed to complete it by edgebugging it, so we know it's possible, but it's not the intended method.