There's already a name for that: An IPv4/v6 network.
Indeed, that is exactly the correct term.
But as a metaphor: I think Jon Postel might have been the first person I heard use the term. I also feel like there was such a picture in some of the early IP documents (like the internet protocol transition handbook in the early 80s) but that stuff I had on paper and it's stuck in a box someplace.
Regardless, it's been horribly abused by marketing people and does need to be dragged out back and put down.
I can't resist slightly getting into it: it was a perfectly decent metaphor until some marketing numbskull heard a technical person use it and decided to stretch it in ways that made it meaningless.
Back when it simply meant, "look, you push your packets into the network and a bunch of routers decide how to get it to its destination without you having to worry about routing" it was fine.