Agree with sm1smom. The field officer's manual is very clear that such a circumstance means disqualification. Either you were told a false story or he presented false documents.
Incidentally if such a case were approved, if USCIS ever figure it out - whatever happened - they can still strip him of his green card. There is proviso that if they discover false info etc on the application they can do that, and I believe this applies even if they have become citizens.
Technically you can't be stripped of your citizenship if they find fraud in your application. However, they can (and do) revoke your naturalization. It is as if you've never been a citizen. This is similar in principle to marriage annulment, as opposed to divorce.