Legally it’s the same thing. The ‘cookie laws’ don’t explicitly forbid cookies, any kind of tracking is prohibited. Also, just storing a cookie with the information that a banner was shown doesn’t require consent. The only thing that requires consent is tracking the user.
Sure it is a thing but JavaScript on that domain can access it either injected or provided by the site. This is quite risky. Cookies can be http only so that client code cant access it.