To support what
@PREMiERdrum mentioned - there are currently two room discount options with broad appeal available thru the first week of October. Yet when I search for availability for either of them throughout September, there are virtually no rooms available at the values, few at the moderates, and plenty at the deluxe level. If I search solely at rack rate, plenty of value options are available. So the rooms are there, just not at a discount from rack, and even then the discount search algorithms cleverly present the highest margin options.
A similar search for next month actually produced a bit more value options under the general public discount (but not for AP) yet Priceline offered the same room(s) within just a few dollars of the WDW site discount price.
That doesn't indicate any sort of motivation to reduce cost to me - in fact, it seems more like an effort to force bookings at full price and preserve total potential revenue.