Well, it all depends on your point of view.
When we talk about NAT in IPv4, we traditionally talk about “real” and “fake”, public and private, routeable and non-routable addresses because we are translating for the purpose of conserving addresses. So there is a meaning to these terms. However, NAT in a more general sense is a translation from one IP address range to another, regardless of whether the addresses are private, public, routable or not. You could translate from 10.10.10.0/24 to 172.16.0.0/24 for example. In such a case, which is fake and which is real? It depends on your point of view.
When we apply this to NAT64, what we are doing is translating between address spaces of two different protocols. Which is real or which is fake depends on the application, on which side of the NAT64 router is facing the Internet and which is not (maybe neither is facing the Internet).
So if we use the conventions of the terminology, then yes, you are correct, the IPv6 address will be fake and the IPv4 will be real. But looking at it in a broader sense, it just becomes a translation in the opposite direction.
I hope this has been helpful!