All has to do with flight number. Lower flight numbers, ie, the ones representing the origination or continuation of an international itinerary will cause the first cabin of any aircraft under that flight number to become labeled as "Business."

This can cause some pretty comical complaints in FC. One day the gentleman next to me asked the flight attendant pre-flight why there were no BE style seats on this 737, as it was labeled business. I restrained my laughter.