Even ECH isn't that helpful. ISP still sees the IP addresses you connect to. Even when non-dedicated IPs are used, I'd be surprised if a quite basic traffic analysis (say, bytes transferred on first visit) wouldn't identify the domain.

VPN providers at the tier of Mullvad should be precise about this stuff -- I think it's more than just a nitpick, considering the audience. oh god did I just use an emdash.

Note that you need some flavor of secure DNS to enforce ECH. The protocol is designed to be downgradable.