But what were a PAX and FA doing out of their seats (or possibly just unbuckled) during a landing?
What makes you believe this was the case? I don't see any reference to anyone being out of their seats or unbuckled, in the report.
______
A chain of errors and misjudgements, but ultimately the captain botched the flare, (possibly due to poor depth/height perception in the dark) - and you just can't do that in an AT. (Well, you can't do it in most aircraft - see SWA-La Guardia - but the AT seems especially prone and vulnerable)