Holding the control modifier key while pressing the "Drop" key ("Q" by default) does not drop a stack of items. Instead, it drops a single item.

What happened:
I held a stack of items (e.g. 64 Cobblestone) and pressed "Ctrl+Q". A single item was dropped, the others remaining in my hotbar.

What I expected to happen:
That the whole stack of items be dropped from my hotbar and in front of my player character.

Furthermore, pressing Ctrl+Q while hovering over a stack of items in the inventory screen does not drop the whole stack either, only dropping a single item there as well.