Recessive/dominant white is a particularly cool one! If you bred him with another recessive white chicken, they'd only have white chicks, even though it's possible none of the grandparents were white.
But breeding him with a dominant white bird could easily result in zero pure white chicks...
Recessive white, perhaps? You'd have to test breed to confirm, but it would behave like that. It only shows up on chickens with two copies of the gene, but when it does, it completely whites out whatever other colours the chicken has.
Edit: looked it up and yep, that's the white that WPR have.