And I got so caught up in my antipathy for your pcp that I didn't answer your question. The only function the gall bladder has is to store bile. When you eat, the gall bladder contracts and squirts bile into the bile ducts, and from there it goes into the duodenum. So after the gall bladder is removed, the bile is still made in the liver just like always, and gradually trickles down the bile ducts instead of being stored in the gb.
But for someone who has had either DS or gastric bypass, the duodenum (well most of it with the DS) is bypassed so it doesn't matter whether you store bile in the GB or not. So the only real disadvantage to having it removed is some added surgical risk and a little extra time under anesthesia.
On the other hand, if you keep a diseased GB, you are at risk for the GB to become inflamed in the future, or for GB "attacks" from stones, which can be very painful, or from a stone getting stuck in the bile ducts. And if you don't have gallstones already, the rapid weight loss puts you at increased for developing them.
I've tried to be even handed here but you have probably figured out by now that I do have a point of view.