Steps to Reproduce:
Create a blue ice floor.
Drop an item on the blue ice.
Use a piston/sticky piston to push item.
Expected Result:
Item slide on blue ice for about 8-9blocks.
Observed Result:
Item was pushed but won't slide.
My English is poor but I tried my best to describe this bug. Hoping for fixing/reply.
This is easily reproduced and confirmed also in 1.16.5. However it's unclear if it's actually a bug. Similar behaviour occurs in creative mode when the player is in fly mode. If a player hovers in front of a piston and it extends, the player is pushed one block, but isn't "launched" by the piston.
However, the behaviour that is sought can be created with slime blocks. If a player or item is in front of a slime block when it is pushed by a piston, the player or item will be given sufficient velocity to move several blocks (either laterally or vertically).
e: This request introduces a conflicting set of wanted behaviours. Certainly, if a player or item is pushed 40m/s (by a piston. i.e. 1m in a tick), we'd expect them to retain some momentum (if not also take damage from the severe degree of acceleration experienced). However, there are now also many documented uses (such as flying machines) where players do not expect them or other items to be given velocity by an extending piston. The compromise seems to be that if you want an extending piston to impart velocity, putting slime in front of it is the way to do it. Piston pushes slime, slime pushes thing or player, pushed item now has velocity and continues moving.