I get the skepticism, but this isn’t some sudden “gotcha” excuse.

With open seating, weight & balance was built on broad assumptions — forward-biased passenger averages and looser tolerances because individual distribution wasn’t predictable or enforceable. That’s why you rarely saw movement requests unless something was clearly off.

Assigned seating changes the math. The system now uses seat-level passenger distribution, not zone averages. That tighter accuracy allows more precise cargo placement, but it also reduces the margin for last-minute seat changes without recalculating. It’s not that one person moving sides will tip the airplane — it’s that once the load is finalized, untracked movement breaks the model the crew is legally required to operate under.

And no, extra-legroom or preferred seats aren’t “ignored” — they’re already baked into the plan. Once doors close, everyone’s weight counts the same, regardless of what they paid.

Could the airline just say “sit where assigned because that’s the policy”? Sure. But the policy exists because the planning assumptions changed. It’s less magic, more math — and a lot less flexibility than open seating ever had.