The bug

Shapeless recipes only check for the correct amount of items in general and the correct amount of occupied slots. This however is not sufficient when a recipe requires the same ingredient multiple times, as can be seen in the attached screenshots.
Either a check for the correct item in each slot, or a general check that no item that is not part of the recipe is included is missing.

Original Report

Video of bug in action

Location of my datapack for testing: 
https://github.com/SamJBarney/Minecraft-Datapacks/tree/master/Redeye
 

I have a datapack that I've been working on that includes a bunch of different recipes, and I noticed that my coarse dirt recipe was giving me dirt for some reason.

Shapeless recipe for dirt: 7 of any crop item (potatoes, carrots, etc), 1 gunpowder, and 1 bonemeal

Shapeless recipe for coarse dirt: 4 of any crop item, 1 gunpowder, 1 bonemeal, 2 bones, and 1 charcoal.

It appears to be tallying up the total number of matching items and using that to select recipes.