The HC issue is prohibiting the open expression of homosexual relationships, not just the heavy sexual conduct. I think they have the strict guidelines to protect young people from wrong paths. Same as age old advice to not sit in a car alone with your date in the dark. Yes, sitting in a car is not sex. It's not wrong. It is a gateway though. Homosexual dating and displays of physical affection go ever further though.

Being homosexual is not wrong. Behaving homo sexually is.

I think BYU wants to leave no ambiguity.