Dropping items out of the Creative mode inventory should now be throttled according to the 24w38a changelog, but this doesn't come into effect immediately, allowing the player to drop many items very quickly for a brief period of time, which can still sometimes duplicate items.

How to reproduce:

1. In Creative mode, open your inventory.
2. Take one stack of any item type and put it somewhere in your inventory.
3. While hovering over the stack, start holding down your Drop Item key (Q by default).

Expected result:

The player would not be able to drop more than one item per second.

Observed result:

The player can drop a lot of items within one second for a brief period of time, after which the game actually starts throttling the item dropping.