Stonecutter eats output of more than 64 when shift-clicking

I created a datapack to make the stonecutter even more useful, allowing me to turn iron blocks into iron nuggets.  Conversion rate being 1 iron block to 81 iron nuggets.

What I expected to happen was...:
When shift-clicking to receive a stack and 17 nuggets

What actually happened was...:
When shift-clicking I received only a stack of my output, the stonecutter "eating" the rest

Steps to Reproduce:
1. Create a datapack that produces more than 64 in the output of a stonecutter
2. Shift-click it into your inventory 
3. This should now "eat" the rest of your output, as long as you do not have an unfilled stack