> So I should cancel one of my pipes because the "commitee" overcomplicated things in the name of autoconfiguration?

That is absolutely not what I said. It’s a more complex setup than a single connection with either protocol, and can be solved with both.

> Which one, the one from ISP A or the one from ISP B? :)

Realistically it is going to return an A record with both addresses, maybe also the link-local one, any works locally. That is a non-issue.