UPDATE: As of 1.21, this now doesn't even work in singleplayer from my testing.

Expected behaviour:

(Singleplayer Behaviour)

When an item is being picked up in your inventory and the inventory closes, the item will go into the hotbar and play an animation while doing so.

Observed/Actual behaviour:

(Multiplayer Behaviour)

On singleplayer, this works fine, but on servers, this doesn't play at all. (Also applies if you put the item in a Crafting GUI and then close it.)

[Look at the hotbar in the attached video.]