Items can enter the player inventory when the whole slots are full.
How To Reproduce:-
Step 1:- Be In Creative Mode.
Step 2 :- Fill the whole player inventory with any items (Stackable/Non - stackable).
Step 3 :- After filling the whole player inventory, go to the creative menu.
Step 4 :- Throw out any block or item to the ground.
Step 5 :- Walk towards the item or block to pick it up.
The block/item enters the player inventory when there is no remaining slots.
The Item/block should stay on the ground when the player walks towards it.
I have a video proof of this bug in this ticket, hoping this information is helpful to fix the bug.