I can understand fixing pistons pulling entities through blocks. Pulling entities through themselves is less understandable but in the end it was a bug. The issue is not in the latest snapshot pistons will still pull entities (except not through the piston) however pistons are no longer able to push entities. Sticky pistons with blocks can push entities but if the player winds up any amount inside of the blocks space (so even if the block is a half slab or stairs that the player is on top of) the player gets retracted with the block and stuck inside the pulled block. I think the mechanic changes were unnecessary and have just resulted in problems were there were previously few.

Screen shots yet to come.