pressing the tit to release the water (as opposed to pressing the tit to pickle the load
This is exactly the point. Pressing the tit opens the hook and drops whatever is on it. If you have a bucketful of water on the hook, you don't want to drop the whole bucket as well. It requires specific wiring to release the plug on the bucket, not drop the bucket.
Many a bucket has been dropped on a fire, or in the dam while dipping up a new load, through finger trouble, pressing the wrong tit.
Certainly just a bystander and no expert so happy to be corrected
Consider yourself corrected.