Oh, there's no doubt it's heterosexual. He is informally quoting someone; "I've heard". I don't think it's fair to accuse him of being 'exclusively heterosexual' in his wording. I mean, true on point of fact, but the phrase connotes negatively, it implies the author is deliberate in his use of heterosexual wording. I think he put enough qualifiers in front of the sentence to not deserve that implication.

As for the idea: I got "be attractive, find someone who is attracted to you, get involved in an intense physical relationship, then make the relationship conditional on them deconverting".