Just remember, if we look at a developmental model for sexual behavior, it's fairly common for teenage boys to engage in same-sex behavior -- perhaps a lot more than we think and/or self-report. Sure, there's a quantifiable "progressive" difference between "genital petting" (e.g. jacking off, showing off size, comparison) and other behaviors such as oral sex, but that's still common.
Of course, yeah, two guys who consentfully blow each other may have a harder time rationalizing that desire with their known/assumed heterosexuality, but there are always exceptions. A straight guy can blow another straight guy if the situation presented itself, whether we're talking teenage fooling around or something like prison or the military or what have you. Perhaps it would entail a lot more forethought ("Would I feel comfortable doing this, even if he is my friend?") and afterthought ("Am I gay now 'cause I did that?") -- unquestionably.
And, of course, if you're young and your friends found out you did that -- yup, you'd be in a world of social hurt.
I'm only adding the comment because, while it's pretty easy to make these assumptions (i.e. jacking off, two guys = heterosexual, jacking off, sucking off = gay as a three dollar bill) and that they work out
some of the time, it's not always the case.
BTW, Horse, go ahead and say that this isn't true, no way, no how, because that's what you usually do on here -- ain't that right, buddy?