You need to move past this statement, I bet you could call every day and get a different supervisor and get a completely different answer. He more than likely said this just to get off the phone because he didn't want to tell you that it is because they value the onsite guests more than they do the AP holders. If you have been one for a while you should know that by now, as "perks" have gone down significantly over the last two years while the price of the pass has gone up. The ultimate "perk" of a pass is that you don't have to pay $100 every day that you visit and that you can go to the parks 365 for $700-$800 instead of the $3000 that you would spend if you went for one day 30 times. Like
@Monty said, the extra 30 days out perk is for getting a room at the resort, just like the 180 +10 for dining reservations, you stay on property, you get the additional perks. But what the non-AP holder does not get is the discounted rooms that you can get as an AP holder, Merchandise discounts, Special AP only events (even though they don't have many anymore), TIW discount as well. There is absolutely no justification at all for an AP holder to be able to book out a fastpass earlier than a guest staying on property when you have access to the park 365 days and have that many opportunities to see the attraction you want to see.