I heard something interesting today
Apparently, the Seat manufacturer that supplies BMW also supplied seats to other German and European car makers.
They think that the (oxide bloom -rusty snowflakes) on their seat base is a reaction to salt crystals in moist air. It could be at the factory (next to a motorway) and/or when their trucks transport the seats to the car companies. They are blaming the salting of the roads in Germany. They say it will not deteriorate the seat frame.
It is something like rust on 304 stainless steel. It only sits on the surface and looks ugly.
I gather this is why BMW is providing the current solution.