Non Stackable items with Curse of Vanishing are able to be stacked in a grinder.

Steps to replicate.

• Step 1. Get any 2 non stackables.

• Step 2. Enchant them both with Curse of Vanishing.

• Step 3. Put them together in a grinder .
  (Sometimes when they go in the inventory they don't stack so keep repeating until they do.)

• Step 4. You can slowly make it into a stack by making another 2 and trying to place the first two onto the other two.