Could be any of of a,b or c. Although I don't think the coatings were applied at the factory but are pretty common, whether dealer or aftermarket. Sometimes from what I gather it's to protect from snow/salt/rust as much as sound deadening. Is the coating new or has it obviously been there a long time? If it's new then I'd defiitely be asking why. If it's old you still need to have a very close look at what can lurk beneath.