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.
There may not be a whole lot of private information in the client subnet, especially since it seems likely that after querying for an A/AAAA record, a client would then send a packet to (one of) the resulting IP(s) and reveal their address, but it's not required to pass it on, and it it seems better to reduce potentially private information passed on.