I suspect one answer to this question is implied by the practice (possibly apocryphal, but I wouldn't be surprised were it true) of dictionary editors inventing non-existant words so that they can prove when someone else has copied their list of lemmata.
Is this another of those cases where what the publishers of the dictionary would like to believe and what we as scholars would like to believe are at odds, however? If so, then until a case has been tested in court, even a lawyer's opinion would be at best speculative. (i'm eager to hear others' experiences, however.)
Best,
Gabriel