I don’t think that wanting a stone means you have attachment issues. I think it just means you want to feel attached to the person you’re disclosing your life to, which is normal and healthy and human. Wanting to feel closeness with another human is not a problem unless the actions we take to get there cross lines — which for what it’s worth, I don’t feel yours did. You literally just held the stone while thinking of him/therapy with him. Sure, he’s allowed to feel however he feels about it, but that says more about him than you in my opinion.
A partial hospitalization program for eating disorders that I went to last year had something that they called a “rock ceremony” whenever a patient completed the program. Basically, the patients and staff would all write (on the rock) a word that reminded them of the patient who was leaving. The patient would then keep the rock with all of the words on it as a reminder of the program and everyone there. I still have my rock and look at it every once in a while when I need encouragement/comfort.
I guess the point of this story is to show that the concept is not all that unusual or bizarre, and your Ts discomfort seems more out of the norm to me. That’s not to say he’s a bad T or wrong for his feelings, but hopefully he realizes that him being uncomfortable doesn’t automatically equal you doing something wrong. I also don’t think it’s fair that he prefaced his story of the stone to the group by saying that you have attachment/boundary issues. I kind of thought the whole point of getting an outside opinion would be to describe the situation objectively and let the group decide, based on the facts, if they would interpret wanting a stone (eta and holding it while thinking of him) as a boundary crossing or not. I hope you can figure out and do whatever is best for you! Sorry this got long lol I always read your posts about your T but don’t usually feel I have good input so I just lurk 😂