This is because there was one IPv6 address in the DNS reply. Search for "happy eyeballs" for the overall description of why. In short - If your IPv6 went dead a

This is because there was one IPv6 address in the DNS reply. Search for "happy eyeballs" for the overall description of why. In short - If your IPv6 went dead and you'd have more than one IPv6 addr in the reply, you'd get bored until you reach the IPv4 addresses.