I see where you're going, but I don't see the legal issue as relevant to my question. The answer I was hoping for was that the company makes no claim toward any rights that may exist in the work the tool generates. That way, regardless of how the law treats generated art, the company won't end up with rights in stuff that their customers made. Compare "royalty-free," which implies the company retains everything except a claim for royalties.
Perhaps "royalty-free" are the terms they're offering if the law does eventually allow an AI (or its creators) to own a copyright.