It is a tough call with dynamic menus that use a hidden div to hide content until a user activates that content and then the div becomes visible. This same process is used to hide text and that is what I'm thinking Google is referring to. There may be many people who get caught in the crossfire if this is something automated.
I have purposely stayed away from using those types of navigation menus just because of the "hidden" aspects of the <div>s. I have many clients asking me why I won't set up menus like that. Well, maybe I can show them after a few updates. I'll take them back to the same sites they showed me as an example and we'll see if they were affected.