While not made obvious in their FAQ, that (48 hour) policy is mainly for price drops inside final payment - you can tell by the language in the FAQ: :"All Royal Caribbean Best Price Guarantee claim forms must be submitted on-line within 48 hours of reserving your cruise and verified by Royal Caribbean in order to qualify for the onboard credit."
All "regular" price drops are an adjustment (lowering) to the price - there's no OBC given. There's no "form" to submit for "regular" price drops. Again, RCI does some things not governed by official easy to digest published policy.