This sounds like pseudolegal folklore (in the US at least). Do you have any actual examples where this affected a case?

In the US, you get copyright on your work automatically, with or without a label.

The only thing a label does in the US is defend against "innocent infringement" defenses. But even that defense doesn't absolve the other party from liability; you just can't recover as much.

There is no reason you can't have `(C) 200X-$currentYear Acme Inc` or whatever.