from my experience with the end of August i can say yes.
i have been there for the switch over from peak to value(or vice-versa) before (mid to late Aug on one trip. and from late Sept to mid Oct on another) and yes, the hours changed from the beginning of out trip to the end. they generally posted updated time schedules at every place where you could pick up a park map (resort desk, on our door, on the windshield of our car when we were camping, at any and every place you could buy something.....)
i don't have my old info handy or i would give you specifics, but yes, it is very strange for it to still be hot and sunny and have the park clear out at 6 or 7.
they scale back how often they have Wishes and Spectro- sometimes only once a week. you can bet that it is crowed on the nights they have these things, even if it is a slower time of the year.
it is still worth it for us to travel this time of year. we hate crowds and are morning people anyway, so leaving a park at that hour is no problem for us.
- lori