I was trying out the new slime block, bouncing about when I started dancing (for the villagers) and took fall damage. After some tests, I found that if you hit a slime block while crouched, not only do you not bounce (which I think was intended), you will hit the block as if it was a normal, non-bouncy block. Also, I believe that it exists in earlier snapshots, but I am not sure.
P.S. If you won't do it for me, do it for the villagers!
To prevent fall damage & not bounce hold jump (Space)