Have also been on long haul flight where captain has put on freight, rather than subload pax, so above doesn't always work.
Utter rubbish!
Captains don't add freight; load control does. No company likes leaving freight, & therefore revenue behind. If maximum revenue means a flight is at maximum take-off weight then 'subload' stuff (pax & freight) gets left behind.
In the case of adverse winds or bad weather at the destination, the requirement for extra fuel can mean freight is left behind. If the captain's instincts suggest that more fuel is needed than the take-off weight allows then load control is consulted to have some weight removed; usually freight.
What I can also say though, is that I've seen captains try
really hard to avoid leaving staff behind if there is
any way to avoid it!
