The word I've heard is that PADI made the determination that instructors could not use Blue Grotto for the deep dive portion of AOW. The insurance company learned this and at renewal insisted that Blue Grotto needed to remove the permanent guideline and add the grim reaper cave signs. There is still a permanent line but it is a cave-style mainline like is seen in many caves, not the large rope that used to run all the way to the back. This all comes first-hand from a knowledgeable source.