Sprinting on a trainer is very unlike sprinting outside. On the trainer the bike is fixed, whereas on the road you can use your arms to a much greater extent to ensure your legs are over the pedals and driving down as hard as possible. I have a 500 watt difference between my all time best ever trainer sprint and my typical good road sprint.
I top out around 120 rpms on the road, probably 115-120 on Zwift.
And going from 600m out isn't a sprint. It's a very long, drawn out effort. I'd wait for inside 200m to go to get max power. Even worldtour sprinters don't go before 250 if at all possible.