it doesn't matter if your dns resolver leaks part of your ip address to archive.is's dns servers when you're about to connect to archive.is from your ip address anyway. the only thing dropping the edns client subnet does is prevent services you use from giving you a server that's closer to you when you do the dns lookup. this performance issue, of course, does not affect sites using cloudflare.
To circumvent this, Cloudflare would have to reverse their global stance or make a special exception to satisfy archive.is.
It’s unclear how we could draw “anticompetitive” from this.