Hi,
I can't remember our previous trip on Etihad but I think every airline we've used have a rule... special needs pax first on last off so yes to preboarding. My wife needs the wheelchair up to the aircraft door but can walk around the cabin when the need arises.She cannot manage stairs so if the airline use a bus gate(rare now) we get taken up to the "tradesman's entrance" on a high lifter.
We next fly Etihad early October so we'll see how it goes then.