This all depends on the listing policy of a blacklist. Some do it for sure. There's no "accepted methodology", it's all up to the owner of the blacklist to define the listing policy.
Some start off with listing individual IP's in a /24 (let's not call it a class C, we stopped using classful routing 20 years ago) and if there are too many problematic hosts within a specific /24 the entire /24 gets listed. Some (possibly other) blacklists choose to widen the range of listed IP's if the owner doesn't take action quick enough, starting with individual IP's (/32's) and gradually increasing it to a /24 or bigger, eventually listing all IP's registered to a network.