If there is a vanilla potion along with the brew during the distillation process, the vanilla potion can be turned into a splash potion for free.

Filter is not consumed after distillation

Paper-1.16.3
Brewery v2.1.2

This is not the case for me. I have put a Potion of Healing in with a Brew and it never changes. The Brew gets distilled and the Potion is not a Splash Potion afterwards.