The plaintiff doesn't want to open a loophole. Suppose that one of these records gets used in a major film soundtrack, and now everybody is downloading it. They will have a harder time asserting their ownership if they don't defend it now.

Their approach stands on applying the law as written: "This is mine and you can't have it, even if I don't really much care about it."

As I understand it: in USA law copyright, unlike a trademark, is not invalidated by failure to defend it. You are free to ignore unauthorised copying of, or usage, of your work until such time as you find it sufficiently objectionable.