Neither of these statements are accurate. Members of Congress sit in coach all the time. If you fly out of DCA on Mondays and Thursdays you will see them quite frequently. Some of them also buy F, though it is the minority.

There used to be a small parking lot for VIPs including Members of Congress but no longer. It was right across from the metro entrance and went away once construction began on Project Journey, quite a few years ago. MWAA waves the parking fees at the regular lot for anyone with a Member plate though, as free parking is part of their congressionally appropriated funding for the airport.