The unknown status seems to mean that there is a roughly 50% chance of survival but many survivors have much lower odds, for example Judith Grimes (TV Series), Kenny (Video Game),(by the way should that be changed to simply "Kenny" or "Kenny Sr."?, the only other Kenny is his son.) and Adam (Video Game) aren't confirmed to be dead but their last known circumstances make their odds of survival very low.

Also I'd like to add that I think a "presumed undead" status would be extremely pointless as that would be overly speculative.