To me this says that you feel this story could be about 'any two guys', which, no. This is definitely a John and Rodney story. If she'd written it about Kavenagh with anyone, I'd have been thrown right out because I don't see anyone liking Kavenagh enough, as presented in canon, to want to have sex with him. If it had been about John and Ronon, or Rodney and Zelenka, then, yes, I could see this happening because of the closeness between those two pairs of people. It's about believabilty, and that has to do, for me, with canon closeness between the characters. If I don't see them having an onscreen relationship that easily extrapolates into the kind of closeness that could motivate them to want to be intimate, the the story isn't believable.