I recently wrote a blog complaining about the lack of VoiceOver support for the Mac App Store (MAS). Apple have responded by showing me how to access the MAS using VoiceOver. So I must apologise that my analysis was incorrect.
My defence is that I am an occasional VoiceOver user and I normally used it to see if a bit of a web page reads correctly. I do that by switching Voiceover on, pointing at the piece of text I want read, then using the arrows keys to navigate the text. This works fine on a webpage viewed in Safari. This method does not work with MAS as pointing to text has no effect.
During the discussion with Apple I was introduced to VoiceOver QuickNav which enables control of VoiceOver commands by just pressing combinations of the arrow keys. For an occasional user, such as myself, this is a much easier than having to learn a series of keyboard commands. This and other VoiceOver functions are described on the Apple web site VoiceOver page http://www.apple.com/accessibility/voiceover/.