I'm sure someone can come up with the details about the lateness, it's a common enough bit of trivia.
As to source, I heard it myself at a con. But what I don't get is why you ask as though this is something I pulled out of my butt when the only reason I'm talking about it is in response to your own words:
but Garrett Wang has been vocal about not getting to do anything on the show (not even directing an episode).
And I say yes he whines about this and you ask me what my source is? What is your source?