I don't see that as malicious. Is my consent record "strictly necessary"? No. Don’t get me wrong. I’m sure they love that, but if sites saved that preference when only necessary was selected, I’m sure a bunch of people would be screaming that they weren’t following the law.
I don't think anything is actually "necessary" if you want to be strict on definitions.
I think it's absolutely fair and unlikely to be illegal to use a cookie to remember cookie preferences. Unless the cookie value was not yes/no, but something like a precise timestamp that could be used for uniquely identifying.
There is no legal requirement to ask for consent for first party functional cookies. The cookie banner is only for invasive 3rd party trackers.
Yes, it is strictly necessary to properly honour the user's choice. Not storing a rejection of consent but storing acceptance violates the GDPR because it creates an asymmetry between the effort required to accept vs the effort required to reject user data processing.
The entire banner is malicious. They don't need consent for necessary or functional cookies. They only need consent to track you - at no benefit to you ever.