OK, I have the answer.
I had restored this setting from a couple posts ago--> CBSubs>Settings>Integrations>Content-Extensions>"Full access granted for :The following ACL groups have access to all content and extensions, independantly [sic] of plans settings:" --> to allow SuperUser access to the world. Your test account is a SuperUser. When I demoted you to a lowly author, the restrictions worked exactly as you said they would. Further, when I removed a menu item from being restricted by the other 9 plans, your plan DID have access to that menu item.
When I log on with any expired plan, it also has access only to the menu item that was unrestricted in all plans.
Thanks for your help on this, Kyle. At least this is good documentation for me. You're officially off the hook and this one is "Solved". I owe you a digital beer.