My gut feeling is that this seller is selling barnyard mix chicks. And, although I do think there is a first generation crossing (Brahma and Wyandotte) that could yield this look, it's proof that they either have no idea what their parent birds are or they're selling hatched eggs and had nothing to do with the breeding. Or, they know exactly what they're doing and they're liars... That happens too.
The chick has the look of good health and unless you were planning on showing or breeding, that's all that really matters anyway.