Not a popular question here, but what's the difference between xcancel or archive.org, and torrents and other pirate services alike?
(except twitter is user content, yet per their tos xcancel is still piracy)
Nitter instances by contrast are specific software intended to view information on a specific proprietary social media website in ways the owners of that website don't want them to. It's a question for lawyers if X declaring this to be a type of copyright violation will hold up in court, but X is also actively trying to block Nitter instances from accessing the site at all, which is a technological rather than legal mechanism.