First, understand that the resorts do not share income. Each has to "sink or swim" on it own. Now into the discussion at hand - why no FD at POR?
Those who believe that this is about the cost of feeding an additional child are just not thinking it through. Forget what that meal costs on the menu, or the price of the
DDP per day. Disney pays a tiny fraction of that to feed you at their restaurants.
The restaurant staff is already paid during this period, as is all other overhead - those costs are static, whether a single person comes into the restaurant or it is filled to capacity. So it only comes down to the cost of the food. Disney buys the food in bulk -
huge bulk orders. So forget what you pay in the grocery store or at Sam's Club - they pay much less.
If I had to guess, I would put the cost to feed an adult in Disney at about $20/day (food costs), but that is probably high. A child eats much less. A family of 5 probably comes in well under $100/day - my wife believes it would be much less than this.
Now consider that their costs to maintain a resort are also fixed. They are paying for everything that you get at a resort whether the rooms are all full or all empty. They absolutely need to fill those rooms to offset those costs.
So, during slow seasons Disney is going to have to offer discounts, and room only discounts just don't seem to be sufficient to fill moderate or value resorts this time of the year. They have tried, with savings of 30% or more at times. Now consider that the average room rate at POR during this season is $200/night (before tax - could be more or less depending on room category).
So, at that rate Disney was already willing to give you a discount of $60/night. Substituting that with
free dining does not cost Disney much more, and with smaller families they might actually make more money.
So the question - why not offer the discount at a particular resort, like POR? Since we have established that food costs are the only relevant factor, the cost to feed a family of 5 vs 4 can be discounted. It just doesn't represent a cost to Disney worth mentioning.
They are not going to let rooms sit empty for $20/day in food savings.