In the US, copyrights are automatic. You can register pieces of work as a way to prove that the work was created at a certain date and time so that you can sue somebody in civil court for damages but the central office is not the mediator for copyright disputes.

It is that registration date that's important, not so much what the author put down as the copyright year. So people that post date copyrights will have a hard time convincing a court that they truly own the copyrights without any other supporting evidence (such as registration, notarization, or other means of proving a date).

And I'm not aware of anyone post dating copyrights years ahead. That would make no sense as copyrights firstly last decades after the person's death and secondly can easily be extended. So delaying the "start" date of a copyright has no particular advantage.