No. all he is asking about as I see it is your consent for him to give info TO the GP.

I am unclear why he needs that consent - he can just send a letter to the GP. The release is needed for him to talk to her two-way ie. getting info OUT of her about you. For incoming information, he does not need a release. I do see his point in having a two-way (or, as Nature suggested, even a three-way) conversation with her and you in the office, but no, it would not give him any rights to direct your care. A completely different document called Advanced Healthcare directive is signed, probably in the presence of a neutral 3rd party witness, to actually give someone the right to make healthcare decisions for you. Your H is not asking for that. He is worried about you and wants to have an input - that is all. I also see Nature's point in that you would be transparent and he probably would both appreciate it and be assured by it.