Actually there are. That's exactly why the tagging exists. In a for instance such as this story, the predominant feature of the story is that it is F/F. That you have some M/F included in it, simply means you tag for that part of your story. For that matter, where it's only a few places, here and there, we have plenty of authors who add the tag as the first paragraph of the affected chapter, rather than adding it to the summary.
I expect I should step this out at some point, so that should the question come up, the answer is perfectly clear.