That’s not really true. The power meter is always the “actual/real” power number.
PowerMatch reads the differential between the power meter and smart trainer all the time in the workout. It finds the differential between the two, and sets the trainer resistance in order to hit the right power target, according to the power meter.
When you start into an interval with 200w power target:
TrainerRoad takes the data from the power meter as the “right” one.
Let’s say the Power meter reports 200w
Let’s say the trainer reads low and reports 180w.
The delta is 20w as the trainer reads “low”.
What Power Match does is read that difference between the meter and trainer, and adjust the trainer resistance unit to hit the target, according to the power meter.
When the power target increases to 250w:
- TrainerRoad increase the trainer resistance by about 20w,
- Then the power meter reports a new power from this adjustment. Assuming the meter and trainer have a different power curve slope (very likely) we might see a 25w differential at this power output (i.e. not a linear 20w adjustment at all points).
- It does this actively and tries to predict the trend via machine learning in effort to keep the target power close via the power meter. The trainer is secondary and set to reach the first goal.
I wrote my example above from memory. Here is the actual Power Match article that likely does a better job of explaining than I tried.