Why did Maya know that Osama bin Laden was in the compound?

In Zero Dark Thirty, surveillance of the compound where the courier lives shows that there are two men and three women. The CIA analysts discuss that there must be a third man living there, guessing that that man must be Osama bin Laden:

George: If there are three females, there ought to be three males.
Observant Muslim women either live with parents or with their
husbands. We think there's a third family living in the house.
National Security Advisor: So this third male that you've identified
as possibly being bin Laden [...]

How can this work if Polygyny is allowed and practised in Islam? Even the movie contradicts itself later: During the attack on the compound, several more women are seen, and the credits list four wives for Osama bin Laden. How could they know that the courier didn't have two wives, for example?

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