As far as I remember (admittedly when a 747 was on the route) there was hardly ever a major shortage of pax seats. But the freight capacity was fully used... So it presumably makes no sense to have a high-density seating configuration that you don't need (or couldn't use because fuel plus max freight leaves less weight for pax). I'm sure a mover can correct that if it's rubbish...
I don't know how the seating allocation is done - I went cattle class down, and six months later got a bigger seat at the front for the trip back (which was the only advantage - not exactly 'business' class!)