I think in this case geocar is implying that you'd only get an IPv6 address. Since vast portions of the internet aren't available over IPv6 it's not a very useful internet.

Some public wifi providers (like the mentioned hotels) hand out IPv6 addresses but don't actually route v6 traffic. So any connections which use v6 by preference will be broken from those connections.

Happy Eyeballs is supposed to make sure that doesn't happen.