It's not immediately clear from the page but this is a NAT style hack for people who don't have normal IPv6 connectivity, and NAT'ed connectivity is inferior to native.
You either mistyped IPv4 as IPv6 or misunderstood the setup. There is native ("normal") IPv6, but no IPv4 except on the NAT64 host. Since IPv4 is almost always NATed for end hosts, it's not inferior in any way.