You do need to consider that many of the workouts were reduced in intensity with the release of Systm.
Although your 4DP settings may have been identical, if you compare the targets in the two workouts you will, no doubt, find that the MAP targets have been reduced since you rode it in July.
As the MAP intervals in AVDP are a significant part of your best 20min power this will result in a lower average power.
As @leebo mentioned. There is a fairly lengthy thread on the subject. One of the responses includes a list of the workouts that were changed and compares the previous and new Intensity Factors.
In the case of AVDP, this was noted as changing from 0.96 to 0.88