Hypothesis (possible spoilers)
I've been thinking about this for a couple weeks now.
If I were the producer of a potentially risky show concerning gay men, I'd want to find a hook that would enable my show to have crossover appeal.
In this case, BMB hinges on the fact that among the gay men seeking James' attention are several straight men. Viewers who otherwise might not be interested in seeing two gay guys hook up might watch in order to see if James gets hooked up with a faking straight guy or in order to simply test their own gaydar.
As a hypothetical producer of BMB, to keep this element of suspense up until the final show, I'd be interested in controlling the outcome as much as possible. But with the ability to eliminate suitors freely, for example, James could eliminate 6 straight guys from a pool of 15 within two episodes, if he got (very) lucky.
However, excepting the first episode, James' elimination choices haven't been freeform. James has been asked to eliminate one person out of groups of three SELECTED BY THE SHOW.
By controlling the group composition, the producer can ensure that it is impossible for James to completely eliminate all straight candidates from the pool. For example, if two straight guys exist in a given group, the best James can do is eliminate a single one, leaving one to continue to a subsequent round. If three exist in a given group, then two are guaranteed to make it to the next round.
Corroborating this information would require looking back at the pool composition over the past few weeks and the eliminated contestants to see whether straight contestants that have been eliminated have ever been put in pools together.
However, the prediction that this hypothesis makes is that Franklin must be straight, because he was put in the same group as Sean (known to be straight) during the round of six.