99% of surveys are flawed, and this article is a perfect illustration of why. I'm betting that the survey instrument (survey questions) was vague enough that a gay man might reasonably say "no" to a question like "do you consider penile/vaginal intercourse to be sex?" because, for *him* that isn't what HE considers sex.
Add in some teenage justifying (I'm not a virgin because he didn't come, etc.) and you get the wonky results the article reported.
That's a big part of my teachings about poly these days. When the boundaries of "sex" are as uncertain as they are, everybody is to some degree polyamorous -- or, at least, nobody gets to pretend that a pledge of "monogamy" settles everything.