Shawn,
A definition like Bastien's, assuming you've remembered it right, is silly, because of course we can never know anything about those hypothetical
mint directives, and therefore, using this definition, we can never say anything about issues!
We can only define issues not from the mint's point of view, but from our own. So, at its simplest: an issue is any chronologically definable body of coinage. How the
mint thought about that body of coinage, and how few or how many directives were required to produce it, is unknowable and therefore irrelevant.
I suppose that Bastein may have defined
his issues in the same way I would, on the basis of
types, imperial titles, issue and
officina marks,
portrait development, and so on, and then simply postulated that each of
his resulting issues was the product of one
mint directive. But such an assumption is pure speculation which is absolutely unconfirmable, so does nothing to advance our knowledge or understanding.