This seems like a tricky question to me. I don't think IC would necessarily mean you can just walk in and expect treatment. The IC seems to me to mostly do away with the requirements of the SoC beyond merely being diagnosed as having GD. The issue with SoC isn't that it requires a GD diagnosis, it's that it requires other irrelevant or unsafe hoops be jumped through.
As to whether HRT would be appropriate without a GD diagnosis, I'm of two minds. I feel like a doctor should be prescribing medications to treat a condition, so I can see the argument that if you don't have a medical diagnosis, it would be unethical to provide medical treatment. But on the other hand, and I lean toward this being more sensible, there are lots of medical treatments that are considered both ethical and elective.
Actually, the more I think about it, I think the latter makes the most sense, if only for the practical reason that some people will self-medicate if they can't go through proper channels. Better to let them through the proper channels than to "protect" them into unsupervised medical treatments.