I would be in favor of eliminating the requirement to do an official post calibration if Duane's method was used and it showed the calibration constant after the course measurement was smaller than the calibration constant before the course measurement.
If the post-cal using Duane's method showed the cal constant increased during the measurement, then an official post calibration would still be required.
I have never used Duane's method because well over 90% of the time the post-cal constant is going to be smaller than the pre-cal constant. So almost always it's a waste of time. In the very small number of cases when my post cal gives a larger constant, I can drive back to the course to adjust. Having to do this 1 or 2 times for every 100 courses I measure takes less time overall than doing extra cal rides for every one of those 100 courses. However, if doing those extra cal rides eliminates the need for an official calibration when I get home for 98 or 99 of those measurements, then it's worth it.