Have I misunderstood this...
I've gone to Back-End Apps and disabled EVENTS - DISCUSSIONS and EVENTS - ANNOUNCEMENTS.... (These are too advanced for my event creators and the basic post comments direct on the timeline will work just fine)
But front-end when the event owner goes to the blue Event Options menu, (s)he still gets the option to Create Discussions and Announcements (and also in the left column there's a section headed "News" which I think is where announcements go)...