I've noticed that James Marsters; as good as he is, can sometimes be inconsistent in his readings of some characters. For example, if you have all of the audio books, go and listen to the Gatekeeper's conversation with Harry in Summer Knight when the Council is about to throw Harry to the wolves, in Turn Coat when the Gatekeeper surprises Harry and company at the dock on Demonreach and in Cold Days when Harry shows up at the Outer Gates. It sounds like three different characters.
It's also possible that Mr. Marsters keeps notes on various characters, and we last saw Mab in Skin Game, she appeared to be disturbed and perhaps angry that Harry threatened to throw down with Marcone if the crime boss didn't accept wereguild for the death of one of his employees, which would have destroyed Mab's reputation. Plus, Mab had been annoyed by Harry's behavior early in Skin Game. So, it's possible Marsters was going off his notes of the most recent past behavior of Mab and Harry and just interpreted her as being more short tempered and angry sounding because she's a bit fed up with her Knight.
I was just listening to an interview with Jim yesterday, and he was talking about how the readers of the Alera books and the first Cinder Spires book sometimes put an emphasis on certain words and phrases which gave a slightly different interpretation of the meanings he intended. Not that it was necessarily wrong, it just emphasized different ways of looking at the characters involved.
