The only far ressemblance with 6to4 is the thing that was actually nice in the design, the automatic word in automatic tunnel. Which for the rest of us means stateless. Compared to CGNATs that is huge.
Beyond that the proposal is not a tunnel and more akin to a nat64 since it allows v6 nodes to talk to v4 nodes. The network can be pure v4 or pure v6 if the method is implemented as a bump in the stack at the wrong end.
Your response is also missing the capability to extend the IPv4 network a million times. Or drop it completely while maintaining IPv4 applications.
6to4 was meant for early v6 to interconnect islands. A solution for a problem that never really existed. Solutions without a problem aren’t usually popular.
Apparently here there’s a real world problem to be solved. Sophisms are of no help.