A good hotel should practice discretion and not make small chat about their guests partners from different visits. Also, it is SF which is fairly liberal about relationships, not just partnerships. Some guests are probably polyamorous or bi.
The comments here indicate a lot of couples book double rooms for amorous activities
http://onemileatatime.boardingarea.c...s-with-2-beds/
Perhaps the hotel's statistics skew towards two adults booking double beds are couples?
You could always call the hotel and just tell them you'll be arriving with your boyfriend, not your female platonic friend. I book travel for my partner and myself under my name and sometimes the details are mixed up. He's been called by my last name, his birthday cake had my name on it, staff wished me a happy birthday instead of him (but they had his passport info!). Sometimes it is better to clarify beforehand if he's the type who minds or would be put off by such mistakes. This isn't a double standard gender thing as I've also known women who ask to be addressed by a certain name or title as well. After all, they're (hopefully) not stalking you on social media so why would they know personal details?