Man to Man Women to Women Or Man to women they didn't say any certain group that was at high risk.
"The rise in oral cancer in the US is predominantly among young white males
Perhaps they didn't ask about orientation to know. Also, lots of folks who identify themselves as "straight" have, shall we say, "experimented", so asking doesn't always tell you much. Yes, you would think that women to women transfer would result in a risk at least as high as women to men, but it's possible too that there were not enough women-to-women transmissions in the study to be able to tell that sort of thing.
Other than that, the researchers appear to be saying that what goes around, comes around.