DNS is hierarchical so as long as the root servers point elsewhere it doesn't matter what they publish and once the root servers are updated then the new servers are the authoritive ones.
Domain registrars, however, usually do not operate forwarding DNS resolvers. They typically only answer queries for zones that they are responsible for, and give you an NXDOMAIN response for anything else. For this reason, nobody would use a non-forwarding DNS as a resolver for their computer since it would make it near impossible to reach hosts on the Internet (unless you happen to query a record for one of the zones they provide service for).