Dropping more than one item when pressing backspace

Sometimes it is possible to instantly drop large amounts of items after picking some previously dropped items up. I initially discovered this when bartering in the Nether but soon discovered that it may actually be a universal issue.

What I expected to happen was...:
When pressing backspace after picking up a number of dropped items, only one item should be dropped as usual.

What actually happened was...:
On occasions when dropping multiple different items and picking them back up, it becomes possible to immediately throw large quantities of an item when pressing backspace once.

Steps to Reproduce:
1. Give yourself stacks of random items after starting a new world in any gamemode, either with commands or through the creative menu.
2. Flicker through the hotbar (pressing 1 then the drop key, moving to another item and dropping another etc etc) and drop each item at random a few times.
3. Wait until you have picked up items and then try to drop one. On occasions, instead of dropping a singular item, it will drop the entire amount immediately once pressing the drop key.