True enough for those of use out riding recreationally or for workouts and/or participated in meaningless races, but, if you're going to try to have championships on Zwift, you need to do better than that. Require some standardized equipment. Require it to be calibrated. Require all riders to weigh in on a webcam pre-ride and keep the webcam on them during the race. Something like that. I wouldn't be surprised if the TdF on Zwift is doing something similar to that (haven't bothered to check).