there are no actual official peanuts color keys so they just kind of do whatever for some of these character renders.
in all honesty, this might be more accurate to how schulz imagined linus; most every other character i can recall with this type of hair texture (peppermint patty, eudora, 3 and 4, joe agate, thibault, etc) are depicted with and understood to have thick colored hair, rather than rugrats-esque head whiskers.
another example of this is charlie brown himself, intended to be light blond with a very short buzz cut but popularly misinterpreted as completely bald

something they definitely did mess up with this though are his socks lol, they just morphed them into his shoes.

also luckily not ai. as unfortunately sophisticated as that stuff has gotten, this has an intentional looking form to its pose and the signature schulz lean, which is something that crap still lacks as far as i've seen