Yes, it could be because Disney cant fill its most expensive rooms.
But maybe -
Converting regular rooms into DVC is an Instant money maker (similar to LLPP) the rooms are already there, slap a label on them and call them DVC and sell them for massive bucks and we already know the nightly rates for a DVC room is insane if one chooses to do so.
Maybe when they are converting rooms into DVC the maintenance for those rooms is also converted to a DVC cost.
Maybe when the rooms that are converted into DVC; those rooms are also moved out of the regular room inventory, could it be possible that a lower inventory can allow them to charge more for the remaining rooms?