I can see where pd2 is coming from. I used to fly various Fokker (F27/50/100) aircraft that would depart with the just the headcount being correct, unless we were very light when we were told something like "nobody aft of row n". Then one day, we introduced loading zones and the numbers in each zone had to agree with the loadsheet. Some people (Flight deck as well as CC) felt they were unable to depart if there was any disagreement between the loadsheet and the numbers of passengers in each zone. Obviously that cannot be correct and I know for sure that many people were unnecessarily moved to make the loading comply with the paperwork. Unfortunately, these people were probably incorrectly told that they had to move for safety reasons. Personally, I performed a trim change calculation to stop passengers being moved without good reason. But, and here's the but - if I determined that a change needed to be mode, it would be done. And the people I would move would be those in the middle and aft. I'll not disturb the premium fare passengers at the front unless I really have to. But if anybody said to me (or my crew) that they were not moving, that would be the last conversation before they left the aircraft. And one or two did.
Would it make a difference if you flew a 40 ton aircraft with one passenger's worth of trim error? Probably not but. But I'm not a test a pilot and have no idea how much margin I have outside the loading envelope, both for takeoff and in flight. The reason I've asked for change is because the CofG is outside the boundary I've been given.
But may I suggest that we may about to have a new reason to move passengers - for fuel efficiency. An aft CofG can save an appreciable amount of fuel and my company are moving towards more fuel efficient loading. The request to move will remain and we'll expect it to be complied with. Only the reason will be different.
PM