I've had this happen before. The agent properly waitlisted you for NF since there are only two classes on the flight. However, since NC = 3, call back and ask for a waitlist for business and not first and voila, you will get the NC seat and sit in First.

I know it doesn't make sense, but I've seen this happen to me before.

Good catch on your part - most people would not look at NC on a two class plane.

Billy