I use a Zwift supported simple trainer, the Elite Qubo Fluid. It seems the power is pretty accurately calculated based on the speed from my garmin hub sensor. I guess Zwift uses some kind of power curve for that particular trainer. My concern is that this power curve will differ based on person weight since roller pressure is not adjustable. Now, Zwift sits on massive amount of data from all users. Wouldn’t it be possible to dynamically improve those curves based on average user data for a specific trainer who also use real power meters? Then divide into several curves based on weight, ie. one curve for 65-70kg, one for 70-75kg etc. Maybe Zwift already do this but I doubt it?
Anyway, more accurate trainers is even more fun when riding in groups and comparing results.