They've tried to clarify some of the changes in updates.
Here.
Among the updates is this...
Anyone else with reviews or shelves created prior to September 21, 2013 that will be deleted under the revised policy will be sent a notification first and given time to decide what to do.
I'm glad they're finally doing something. I hate it when people use book reviews to rant and rave about everything but the book.
I do think they should just make all shelves private, so no one else can see what they're named. That would have been a lot better than deleting them.