Because of the way they look, and they are not a true white marking, they have more of a roany look to them..let me find the head on shot of her...you can see her star and the difference in color. Even well taken care of horses, like that saddlebred, can come down with fungal scarring.
Fungal scarring should turn the hair white, though, shouldn't it? Looks "off-white" in the head-on pic...unless that's just the difference in skin color beneath. But that doesn't really seem to be the case.
I see a roany look to the Saddlebred, but to me, these gals' are very well defined markings with clear borders.
I can find more fungal scarring that have more defined. And no, fungal scarring won't turn it white white. More like an off white. My SSH mare has a small spot on her black, and it's off colored from the rest of her. It was from ringworm.
They even think that lacing on horses is caused my fungal scarring of some sort.