If you were able to complete all the Zwift Academy workouts (without changing the “bias” downward whilst cycling), then your starting FTP was fairly accurate (if not low). If you found that you had to drop your exercise bias during your Academy workouts in order to successfully complete each interval (with a gold star), then your starting FTP estimate was probably erring to the high side. Perform the same FTP format evaluation (in the same rested state) after every 500-1000 km (monthly?) to zero accurately…
Cheers, @wesfree