Pick block changed to a keyboard key doesn't fill inventory slots when dragged

The Bug:

If you change the Pick Block control from Middle Button to a different button, you will lose the ability to pick-block-drag an item to fill multiple slots. Middle Button won't work at all, and the new Pick Block key can only clone items on press.

Steps to Reproduce:

1. Change Pick Block from Middle Button to a key on the keyboard.

2. Get an item in the inventory.

3. Open inventory or container.

4. Take that item via your cursor.

5. Click and hold down the new Pick Block key on that item.

6. Drag the item across the inventory or container to fill up slots.
   → ❌ The slots will stay empty.

Observed Behavior:

When attempting to drag an item across the inventory or container using the new Pick block key, the slots remain empty.

Expected Behavior:

The new Pick Block key should allow dragging an item to fill multiple slots in the inventory or container as Middle Button did, without leaving the slots empty.