Where would they have ended up if they forgot to lean it during the cruise?
With not quite as much of the 45 minute fuel reserve they are required to carry. However, that 4 minute reserve is to be at "normal cruising speed", so certainly, once you realized that you were tight for fuel, you'd slow way back to best endurance power setting, and make the most of what you still carried.
That requires being "ahead" of the plane, and your flight as a whole. I'm not sure that was happening well for this flight....