As for post-dating a copyright claim. Um, is it an infringement of a law to make a claim where the law requires no claim?

Yes, it is. True, the law doesn't require a copyright claim, but if you do make one, there are certain rules you have to follow. One of them is that the copyright claim on the item has to be on the year it was first published in.

As I noted in one of my other posts in this thread, post-copyright claims are extremely widespread in the entire publishing industry on items published near the end of the year. In my high school German class, the teacher had just ordered recently-published books at the end of 1999 with a copyright of 2000. Illegal? Yes, but hardly something worth boycotting over.

Update: Fixed ugly grammatical errors. Must make better use of preview.