But they have absolutely no way to prevent any big AI harvester from harvesting this content, so whatever they claim has no impact whatsoever on what data gets harvested.

Am I missing anything?

I have heard the term DNS a million times but don’t really understand it.

Learn about DNS, it’s the glue that holds the internet together, any time you spend on learning more about DNS will quickly pay off. You probably already know that it’s what maps domain names to IP addresses and vice versa, but it can be used for loads of other useful things too.

(My own two favourite not well known but totally standardized really convenient things to use DNS for is to provide SSH host key fingerprints through DNSSEC and requesting letsencrypt certificates for host names without any webserver.)