Fair enough. I presume the reasoning is less mass so the worn clutch will cope better? I think though that the inertia of the rotational mass is a much less significant load on the clutch than the load of pulling the air. And for fans of the same design, whether plastic or metal, they will present the same work load.
Just some musings - I don't know off hand what the 280E fan looks like. I presume it is similar to that in my 280SE, which has a much smaller centre boss and clutch than on the 450.
Ryan