No, it feels like the standard 'group/engineer/PM' didn't think anyone did anything different from their own implementation.

Lets Encrypt is just used for like, webservers right, why do this other stuff webservers never use.

Which does appear to be the thinking, though they blame Google, which also seems to have taken the 'webservers in general don't do this, it's not important' - https://letsencrypt.org/2025/05/14/ending-tls-client-authent...