I feel like it's inconsistent with how buckets normally work though - you don't get an empty bucket when you place water in creative mode, why should the cauldron be different?
This is intentional - you need to use a comparator to get the signal, it doesn't just come off the cauldron
https://minecraft.gamepedia.com/Cauldron#Usage
I feel like it's inconsistent with how buckets normally work though - you don't get an empty bucket when you place water in creative mode, why should the cauldron be different?