Look at the map of Scholler on the Airventure web site and add the 24 hr generator and water/electrical sites, and compare it to the rest of the campground. Maybe it's not 80 percent, but certainly well over 50 percent.
Also, looking at the map, they have converted the area just north of Camper Registration to a parking lot. Never camped in that area so I don't know if the whole area that's now parking was available for camping before, but at any rate, it is another reduction in the area that is available for tent camping.
I think the water/electrical hookup area has been expanded as well. I don't remember the area just east of the Red Market Southwest being water/electrical hookups last year, or that it went as far east as Doolittle Road. But OI might be wrong about that. (Each of those sites generates about $2k, compared to $300 or less for most of the regular sites.) (Based on having to pay for the water/electrical sites from the date of reservation, and anecdotal evidence that most of them are reserved on the first day they are available, and most regular sites being used 10 days or less.)