Re: I've said it before and I'll say it again
Those things are the backwards compatibility. How did you expect it to work? Magic?
v4 isn't forwards compatible to address spaces wider than 32 bits. That's not v6's fault; it's v4's fault. There's no way to make it "just work" without some form of backwards compatibility method, and that's what v6 implements -- because it's the only thing that's compatible with v4.
If you think I'm wrong about this, all you need to do is explain how they should've designed it to make it possible for a v4-only device to talk to a v6-only device. If you can describe a way to do it, you'll prove I'm wrong. Just remember that whatever you come up with needs to a) be something that v6 doesn't already do, and b) actually work.
I've asked a lot of "v6 should've been backwards compatible" people to do this, and not one has been able to. Perhaps you will finally be the one to share the secret...?