Usual non-enchantable tools dont work properly with the enchanting table

Usual non enchantable tools in the enchanting table dont work properly when they are assigned as primary items for enchantments, both custom and vanilla. 

There is provided a datapack with a custom enchantment, cleansing, for a brush. 
Notice how you can merge it with an enchanted book, yet the enchantment wont appear if the brush is placed in the enchanting table.

Note: in this datapack this applies for the brush, but this seems to be the case for shears, carrot on stick, and warped fungus on a stick.