Of course that doesn't guarantee Putin wouldn't use tactical nukes.
Point is i think, at least it should be considered by you, that it's more than likely no one but Putin and you and others worry about Putin's threat. If that's the case it doesn't exist as a possible blackmail tactic. And the case actually is that the West is actually going along as though he never said it. That's the likely situation, i'd say.
It was Plato who said, “He, O men, is the wisest, who like Socrates, knows that his wisdom is in truth worth nothing”