The Bug:
minecraft.used:minecraft.water_bucket doesn't increase when filling a cauldron with a water bucket.
Steps to Reproduce:
Create a scoreboard objective for tracking the use of a water bucket and set it to display on the sidebar.
/scoreboard objectives add UseWaterBucket minecraft.used:minecraft.water_bucket
/scoreboard objectives setdisplay sidebar UseWaterBucketFill a cauldron with some water using a water bucket.
→ ❌ Notice how the scoreboard doesn't increase.
Can confirm