Will this work for IPv6?
replies(1):
http://1.1.1.1 redirects to https://1.1.1.1 which then redirects to https://one.one.one.one
but the TLS cert on https://1.1.1.1 (or https://[2606:4700:4700::1111] on ipv6) is still valid for the ipaddress otherwise your browser would put up a warning during the tls handshake.
Also (and just speculating here), it could be they wanted to get away from promoting https://1.1.1.1 because of legacy spam filtering. But that’s just me thinking out loud as to why they would prefer the domain over the ip