I think they mean from a user perspective. As a user I can create an account with a provider(be it google or myself), but I can't migrate that account without l

I think they mean from a user perspective. As a user I can create an account with a provider(be it google or myself), but I can't migrate that account without leaving a forwarding address at the original address. The alternative would be storing the user data on a distributed data structure(like a pki network or distributed hash table) so that it's not tied to a single provider.