Could have been:
1. Landing wt restriction at NCL. If the weather goes cack (which it can do in NCL with very little notice) the a/c is limited to the Cat3 max landing wt. I don't have the perf manual to hand, but I remember it is quite restrictive.
2. Some a/c defect leading to a lower than normal weight restriction.
3. They may have been carrying round trip fuel (for economy), up to normal max landing weight. In which case getting staff on comes second to saving dosh.