its used to be called "peek-a-boo" muscle. good observation with the sport today compared to 20 yrs ago. some say it has something to do with a certain drug(s) that keeps the muscle tonus at a higher % at all times, ala looking flexed when relaxed and no shape/size/look change of the muscle when flexed. as others stated has to do with training also, fiber types trained & so on.
