I don't think it's far fetched. We know very little about the inner social workings of deer behavior when it comes down to it. The fawn needed an adult deer to look after it. Came across the 3pt and followed him around. The 3pt tolerated the fawn and now probably is comfortable with having him around. Even a buck would know a fawn from an adult deer. Maybe he did kinda take him under his wing knowing it was a youngster.

I have cam photos of two fawns with a group of bucks over a two week period. No does anyhwere around them.