However, according to the Cloudflare FAQ, it should not support ECS.
1.1.1.1 is a privacy centric resolver so it does not send any client IP information and does not send the EDNS Client Subnet Header to authoritative servers.
Try another tool provide by Google. It shows that 1.1.1.1 doesn’t support ECS (no any ECS information responded).
1.1.1.1 is a privacy centric resolver so it does not send any client IP information and does not send the EDNS Client Subnet Header to authoritative servers. The exception is the single Akamai debug domain whoami.ds.akahelp.net to aid in cross-provider debugging. However, Cloudflare does not send ECS to any of Akamai’s production domains, such as akamaihd.net or similar.