Power = torque x angular velocity (cadence)
Virtual power simply equates a wheel speed to the power required to sustain that wheel speed, AFAIK it doesn’t take into account the power required to accelerate up to that speed. This calculation has a big drawback because there is a hell of a lot of momentum in the flywheel and the bicycle wheel, once up to speed even it keeps turning and displaying big power number even when you have stopped pedaling.
It also depends on how accurate the power curve is for your trainer. I contacted the minions after I found a ceiling of 316w on my trainer at about 50kph wheel speed (which I can get to in the small ring), their answer was that they only had data for my trainer upto a certain speed so above that it just continues to display the same power. Their advice was to use a higher level.
In my next FF I moved the resistance level on the trainer and in the app up to lvl 9 and recorded a new 5sec best of 1765w (+1320 on the flagged and adjusted value from before). This changed my rider type from time trialist to sprinter
I am under no illusion that I really have a sprint that huge, I would go further to say that I would only trust a sprint power figure that comes from a power meter that uses strain gauges and angular speed sensors or has a calibrated flywheel (Wattbike, ConceptII BikeErg) so the trainer’s computer can calculate the instantaneous power required to accelerate the flywheel.