I'd say that TopperHarley's Airbus case, there is more weight outboard laterally (longer weight moment arm).
due: full wing tanks in the first hour of flight. This would increase dutch roll inertia.
In aviate1138's 757 case on approach there'd be more drag outboard laterally (longer drag moment arm) due: greater drag on approach configuration.
Does "the software" automatically change y-d sensitivity to suit changing tank levels and/or a/c configuration?
"I know anuff to learn"