Indeed, what a coincidence! Maybe somebody looked at the 6 pax and couldn't find any combination of 2 that were below 120 kgs (as would be the max allowed combined mass of the 2 front pax).
However, there is nothing a responsible operator would do differently based on the AD than before. And there is no change of procedures, which the AD prescribes, that were not in force already. It basically says, do a W&B based on actual and true pax mass before (each) flight.
You don't need an AD to compute the moment-arm of the front pax ... any spreadsheet or flight planning app allows to do this, and to introduce new stations as required.
Apparently, however, in the tour business there have been too many incidences where this was not done. Quite strangely so, as in the tour business the circumstances (route, density alt, fuel requirements) are always the same, and it should be very easy to manage the only true variable (the number and individual weight of your pax).