I’ve never signed anything like that but I’ve never had a T who didn’t allow contact between sessions.

I’m obviously not a T, but I think it would make good “business sense” to put it in writing along with all other office policies. I can’t remember what I signed with my current T but I do remember a paragraph he has in that if you abuse him or his family members he will terminate immediately. It was a pretty thorough document; I actually edited and proof-read it for him before he implemented it, but I don’t recall anything about contact, maybe because he allows it.