Here's a map of the helicopter routes in the area. In this case, they were flying on route 4... https://www.loc.gov/resource/g3851p.ct004873/?r=0.67,0.258,0...
Yes, this group transports VIPs and sometimes does so in secret. This training flight was a "simple" check-ride for the pilot (simple in scare quotes because part of the ride was using the NVGs, which strikes me as fairly ridiculous in the DCA air space).