I think that, to a certain extent, it depends on how many different genres they involve themselves in. Miller and Sheehan have not really strayed far outside their chosen (and fairly specific) genres. Compare that to someone like Pino for example who has played with lots of acts over the years. Although his fretless work is pretty easily identifiable, his playing on fretted basses is less so. And does he always sound like Pino? In style maybe, but not in tone I wouldn't say. Same goes for people like Bobby Vega and numerous others that I can't be bothered to think of...!