I looked at another week in August and it too had the 15% off on it. I think it very well could be the Disney+ discount already applied. With an Orbitz coupon applied, they could be cheaper option.I've gotten deals on Priceline like that recently.
I need just 9/23 after our 4 nighter on the Disney Wish, but Disney isn't a fan of the "orphaned" night. If I pair it with the night before or after I can book that night. I really wanted a Disney hotel, but may have to do the Swan on an express deal through PL.