the fact that they never talk about MC when they stay with each other, some doubt....
the point clearly is that it has to be this way because the only possibility has to be the trouple and no couple relationship
but you are right that MC in theory could have made things go differently both on the night of Josy's arrival and afterwards in his future room, splitting Maya and Josy's couple for sure and possibly taking advantage of them. instead he runs away first by giving the girls a chance to reconcile (I don't think Maya could take any anecdote about Josy well at that moment) and afterwards by establishing that all guilty equals no guilty without ever expressing a preference peer to one or the other