I feel like Buzz must have a higher capacity than Peter Pan. The Omnimover style rides are usually great at cranking through the crowds. I tried to find some information, but all I saw was the 800 per hour number. That same site though has Haunted Mansion putting though 3,200 per hour. They can't be all that different, can they?
So, I don't know the actual way the number was determined, but I can throw out a few facts:
Buzz is really only set up for 2 people per car, while Haunted mansion can handle 3
I "feel" that haunted mansion cars move faster. No scientific facts behind that one.
No matter what the real number, I guess my point is that to handle more crowds, I think they need to address how many people can be entertained at the same time. Having a ride that can handle twice as many people as the previous ride is in my opinion a good thing to consider.
Don't get me wrong, I love the nostalgia of many attractions, and I hate to see them go. I wish that Disney would basically take a "Circlevision 360" movie of every ride. Then build that into one of those stand alone simulators. Then they could put those simulators in malls around the country. For $5, you can ride any "ride" that you want, and the back of the ticket will even get you $5 off a one day park ticket. Want to ride space mountain, Peter Pan, or even the old Skyway, which could be simulated with a drone recording and a little CGI...
Anyway, back to my point, this is not a new thing for Disney. 20,000 leagues was a very slow loading ride, that took up alot of space. The new mine train takes up only part of that space, and handles way more people.