wow - that is just wrong, trying to get him to give up the extra seat.
I was once on a flight where I had paid for my wife to fly and she had the seta next to me, and said "well, since my wife paid for the seat and she is not here I can expect that it will be empty, right?"
Wrong - they said she had to be on the plane to claim the seat (or at least check in) otherwise I gave the seat up. But do I get a refund? no.
Of course not.