> It’s important to remember that DNS64 and NAT64 are meant to be enabled for IPv6-only subnets. If you enable DNS64 on a dual stack subnet, then your dual stack instances will receive both A and AAAA records for the same IPv4 destination address. The OS-level settings will choose the preferred protocol, which in most cases is IPv6. Therefore, the communication will flow through the NAT64 gateway instead of using the IPv4 protocol directly.
https://aws.amazon.com/jp/blogs/networking-and-content-delivery/dual-stack-architectures-for-aws-and-hybrid-networks-part-2/
はははー完全に理解した