It's not NAT64 or 6to4. An ipv6 host doesn't own such an address; it goes to a relay, and the v6 host is using a random unrelated v6 address. The ipv5 thing is ipv6 natively using ipv4 /32s.
So how does an ipv4 host address an ipv5 host that has a 64 bit address
So how does an ipv4 host address an ipv5 host that has a 64 bit address