Ryn operates with variable MTOW: 66,990; 69,990 and 74,990: you just need to declare which one you use prior to operate the flight. Most of the time the ATOW is well below 66,990 because the commpany is operating short flights, with almost no bags in the hold and little fuel tankering.
So there is no massive fraud on en-route fees; maybe few flights had discrepancies due maybe to omission or little coordination between crew and dispatcher or else. but there is no chance a fraud system has been implemented as most of the flights have ATOW around 62 to 64T so no need to fraud!!!