Fleece is "a general term for a soft fabric (often with a deep pile)"
. I've never seen polar fleece or any other similarly man-made materials that weren't 100% synthetic. In fact, I think but am not sure that the manner in which polar fleece is produced makes the inclusion of wool impossible, but I can't remember where I read that. As far as mislabeling is concerned, highly unlikely, as to do so is actually illegal.