I had seen this thread the other day and was curious about it myself... I needed to run out to the storage facility today and try to track down a leak on my 2012 21SS, so I took a tape measure with me.
Mine (with tongue level and properly inflated tires) is 9' 4" from the ground to the roof line (measured at the tires). I meaured the other side also to make sure there wasn't something weird going on.... Also 9' 4". My AC is a Coleman Mach and it is an additional 14.5".
So mine is 10' 6.5". Measuring from the ground to the top of the kitchen exhaust vent is about 9' 10", so I suspect that is where FR is taking the 10' number from.