Slime blocks at y 72 can't be pulled if on top of two adjacent sticky pistons in pre-1.11 worlds

If you put a slime block at y 72 on top of a sticky piston and push them with 2 other sticky pistons, when you try to pull them back the slime block will not be pulled back.

This only effects worlds created before 1.11 I think. It doesn't effect newer worlds