I'm talking purely about DNS, and in fact I wrote explicitly that "HTTP can multiplex multiple sites on a single IP address", because the problem exists only at

I'm talking purely about DNS, and in fact I wrote explicitly that "HTTP can multiplex multiple sites on a single IP address", because the problem exists only at the DNS level. A compounding issue is that CDNs (or GitLab/GitHub) want to be able to change their IP addresses, so they don't want you to use an A record.