I was building a contraption recently involving an automatically-activating dispenser (using a comparator, NOT gate, and timer to automatically fire it whenever it contains items) and as part of testing it I was putting random things inside of it. Since I didn’t have a better location for it at the time, I was building it in my Nether Portal room. I happen to keep a fire-proof, blast-proof chest nearby the portal - tools and armor for adventuring, matches for lighting the nether portal, and a GT6 wooden bucket filled with water for putting the portal out when it’s not in use.
One of the items I tested the machine with was the water-filled GT6 bucket. When I put it in there, it just shot it out of the dispenser like it would any other item. I didn’t think much of it then, but later I remembered that when you do the same thing with a vanilla iron bucket, if the bucket is full it will try to place whatever fluid the bucket contains in front of the dispenser, or if the bucket is empty and a fluid is in front of the dispenser, it will try to store the fluid in the bucket.
Admittedly, using the dispenser in this way is pretty situational (e.g. building a mechanism to put out the Nether portal as previously mentioned, or a mechanism to say, sweep the floor of a dark room full of mushrooms) and already works with iron buckets, but being able to do it with GT6 Wooden Buckets as well would be a nice feature to have as well.