My workouts in TrainingPeaks set a power range for long intervals (eg: 125-165w for 60mins). When they appear in TP Virtual, the ranges are changed to slopes (eg: start at 125w then gradually increase to 165w over 60mins).
I'd much rather ride these intervals at a fixed power using ERG mode rather than have it gradually increase or decrease.
Other platforms deal with this by using the middle value of the range as the set power for the entire duration instead of using a slope.