I don't believe there's much of a track record for private crafts reentering from orbit, intending to be recovered. Most private crafts like communication satellites breakup on reentry and don't pose much of a risk to ground population. This station was designed specifically to survive reentry intact. I'm not sure what kind of deorbit equipment that station has but I would guess that's what the FAA is concerned with. Any failure of navigation or propulsion during deorbit could result in the station losing control which would have it crashing down in some unpredictable point and time along its 25,000 mile path over ground. Undoubtedly there are some large populations below the orbit of this station