This is spot-on. Furthermore, such a lax definition indicates that certain hypotheses will have "probability" zero. If our language is English, the explanation, "PUJF;FDAS!;FDS?" could be assigned probability zero. While this does not guarantee that the set of possible explanations is finite, neither does the author prove that the set of nonzero possibilities is infinite, and if it is not this proof is largely useless.

Also, interestingly, the rules do not address the, "A wizard did it!" problem with complexity, though that is likely far beyond the attempted scope.