Wow, I have an unfixed bug in the 20,000 range but I'm impressed that MC-4 hasn't been fixed yet.
Still a problem in 1.8
This is still a problem in 14w31a. I've updated the affected version(s) and added more screenshots to confirm.
I also noticed this occurs; it happens with me too, every time. Same goes for sprint-jumping. My guess is that Minecraft calculates that the player jumps before it calculates the slime block, so the slime block doesn't happen if the player is moving upwards, that's clearly wrong.
That was a completely unnecessary change. The bug has been confirmed many times and it's very clear what's going on. You're just changing details to other similar details.