That's true, but this bird is full grown and the crests of males and females are very different. A hen's will have rounded feathers, like this girl's, and the shape in general is round. A Polish rooster's crest will have long, pointed feathers just like the saddle or hackle feathers. A rooster's crest hangs down and isn't round in shape, but more flowing.Tail feathers will tell you the gender at that age. If they are long and curly its a roo, if they are straight and flat its a hen.
It looks around 8-10 weeks old. I'm thinking it's still a little bit young to sex, but the lack of any pointed saddle feathers make me lean towards pullet.