In future I will definitely mark up the audio in advance, I've only just moved to CS6 and was working on my first learning project and hadn't marked up the audio because I had intended to do it as I went along rather than all beforehand to allow me some flexibility in interpreting the beat as the video evolved. Previously it wasn't a an issue as I could do it.
It just seems strange, I can't imagine it to be deliberate. The audio playback freezes when you hit M, it doesn't drop out of playback mode. I can't see why the programmers would want that. Likewise why would video/audio clips work fine but not audio only?