I don't fill that info out. When the clinician asks in session, I tell them I don't want them in contact with each other. Since I've moved though, it's been easier. I don't actually have a PCP in this area... Though I don't think any of the T's here have asked about it.

You certainly have the right to leave any part of those forms blank. They can't demand you answer it, and they can't demand you to give permision to contact anyone else.