Organized events where all participants (1) use the same model of trainer and all are verified/calibrated as part of the event and (2) weigh in before the event are the only way to have a "legit" race.
Outside that, there is just too much that can skew the results. I'm sure there is a lot of cheating/fudging/Hope Hicks white lies/willful ignorance at the top of the food chain among the top racers, but even more than that there is a TON of true ignorance (I use that term in its literal sense, not as a pejorative regarding intellect or character) among the Zwift masses regarding power numbers. There seem to be a lot of Zwift/trainer users who have no experience with an accurate PM on a bike outside IRL so that they know what, e.g., a "real" 300W feels like. I recently saw a female rider who was excited about her recent FTP increase to ~4.5W/kg. I then clicked her FB profile and she was approx 50-60 years old, a grandmother, and looked approximately 5'6" 175lbs and not athletic.
Just to be clear, I think it is awesome that she is on the bike getting in good healthy exercise, and I'm not body shaming here. What I am saying is that there is no way that this particular individual is 4.5W/kg. But she absolutely thinks she is, she truly believes she is, because that is what her trainer is telling her and she has no frame of reference to know that her numbers are not accurate.
Or maybe she is just the Zion Williamson of cycling, a generational freak who can do things no human with her body composition should be able to do. If that's the case, there seem to be a LOT of Zions on Zwift.
Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152 https://vimeo.com/user11846099