You're assuming that he didn't speak to anyone about it. That seems like a stretch to me.
Why not mention what they told him? And why are they so quick with the payment when it is on a blog, but not when they employ talks to them directly? It has the feel that his blog post was the first they heard about it. It also has the feel that Kasten didn't like him and wanted him to quit and was paying him late on purpose, and he got forgoten about in the change over.
Either way this is a big bungle from the business side of the front office. Which is actually worse than baseball bungles as I have heard the Lerners know how to run a business. Of course they are also used to dealing with contractors who never pay anyone on time.