Mt. Mitchell has actually lost a foot--probably due to the new observation tower construction (this makes sense--remember the NC Highway Commission BM atop the boulder on Mitchell's summit? it got blasted away for the new observation tower, being in the way of where the ramp begins on the present day tower.). LiDAR data in 2009 determined the summit to be 6683 ft., with an error range of only inches. LiDAR data (which is not satellite) can indeed differentiate between natural and manmade surfaces after the data is "scrubbed" by the analysts.
The datasheet does say 6699 for Mitchell #1, however, the datasheets also still list 6720 ft. as the elevation of the top of the former stone observation tower removed in 2006. We know that tower to be 35 feet tall. The math tells us that that datasheet (Mitchell #2) puts the ground summit at 6685, right near its known elevation.
The current datasheet for Mitchell #1 may reflect the elevation of top platform of the new observation tower, which is about 15 feet above the ground, if the mark was adjusted recently.