The Comfy Chair

What we're saying is that the situation isn't sufficient for them to have had sex without the bond, and, whether the situation is foregrounded or not, to zero in on that as the primary reason for them to have had sex is over-focused. Without this situation, they probably would never have had sex. Without the bond between them, even this situation wouldn't have motivated them to have sex. They're equally important. You seem to be discounting the bond and focusing on the situation, but I can't disregard the bond or see it as subordinate to the situation in any story where people choose to have sex (that isn't a PWP.) They don't have sex because of the situation; they have sex because they're in this situation and they have this bond. Without either, it wouldn't have happened. I also think that, in a story of this type, whatever characters are appearing, the bond will remain subtextual because of the guys being straight, because their straightness is central to their appreciating the female body they're with. They're a sort of unreliable narrator (though they're not actually narrating), not consciously aware of the bond as a motivator to their actions, but the evidence for its presence is in the action, itself and the choices they make. It doesn't make the bond less important than the situation because it's not evident to them, early on. And that would be true for any characters who could believably be seen in this situation.