Minecraft Version: 1.10.2
Inventory Tweaks Version: 1.61-56-a1fd884

Potions are described as automatically refilling in the documentation, however, this feature does not work. I tested this in a creative map, with no other mods interacting with it. Pickaxes do automatically refill, but potions do not.

Probably fallout from Mojang's messing with potions in 1.10, they only work at all due to having to last-minute build a new feature.