There does not seem to be any impediment to anyone of any nationality, including space tourists, visiting any part of the ISS, so color me doubtful on that theo

There does not seem to be any impediment to anyone of any nationality, including space tourists, visiting any part of the ISS, so color me doubtful on that theory. People do seem to avoid the cramped Russian side mostly, and who knows what goes on socially that NASA PR hides from us. Anyway, the US military has their own, apparently unmanned, shuttle replacement and do plenty of launches of secret stuff on conventional rockets. This is not surprising when you consider the relative budgets. Disposing of the station's trash seems a large enough logistical problem that getting one more shuttle-load out could be the real motivator. Sorta sad to think that the last shuttle will be essentially a garbage scow on landing. At least they didn't stuff it to the gills and send it down to burn up on reentry, like is done with the majority of craft that dock to the ISS.