There was a question today on the behavior with the update in http://support.microsoft.com/kb/2415902 which adds further text to the presence states for IM Only and No Voice.
The question is why are the text phrases different and the reason is we are using “positive/negative” phrasing of capabilities. If you are Available, we indicate the possible mode. If you are not Available, we indicate the impossible mode.
We are looking to add this tidbit to the article in the hopes it helps you communicate with your teams.