This is news to me, maybe I missed an announcement somwhere.
You used to be able to book up to 3 rooms on a single AP at the AP rate. Now each room booked at the AP rate must have an AP holder staying in it.
I had two rooms booked at the AP rate for end of Sep, on my AP. My friends sister thought she might come along if she could get a good room rate. I tried to book another room for her, and was told that this new policy went into effect "about a month ago"