[twenty twelve]Can't make a voiceover accessible menue in the default template

The menu structure in WP’s builtin themes (twenty eleven, twenty twelve) does not allow navigation through multilevel menus. I set up a small site at http://twentytwelvemenuaccessibility.wordpress.com/ to show the issue (there is a second level menu under “the specification”). If you’re on a mac with voiceover, you’ll see/hear that the voiceover does not go into the second level menus. (the menus are there with a mouse, but voiceover does not go into them.

I will note that other themes do this properly, so it’s not the browser or voiceover. See this studiopress theme as an example: http://demo.studiopress.com/news/, even if the menus are tedious as demonstrations.

The testing environment is Mac OS 10.8 with Safari or Chrome (and Apple’s voiceover).

Is this an issue with the template, or my setup. I’ll note that I’ve just done very simple menus with this demonstration website.