This slightly differs from my understanding - although whether or not you calibrate should be largely irrelevant either way.
Without getting into the the technical differences between how it works and how you describe it…here is why I think the calibration frequency or even overall accuracy of the trainer matters with power match.
Essentially calibration of a kickr is handled via a spin down, which is measuring the resistance applied by the belts in the system - it then applies this as an offset to build the entire power curve. It doesn’t do anything that would change the slope of that curve, just the height of it from zero (could be positive or negative depending on the spin down results).
What powermatch does is receive the power from the power source being used as a primary source (either the trainer or a separate power meter would use the same principle) and then adjusts the resistance based on that number compared to the target power.
So if the power source is 305 and the power target is 300 watts the application will transmit - reduce resistance by 5 watts. It doesn’t matter if the power source is the kickr or the power meter - the application is doing the same thing.
Some people struggle with power match not because the software takes more time to calculate this data or that the math is more complex - it is that the power readings are coming from closer to the power source so can be much spikier. This is particularly true for single sided power meters where the power meter itself is doing some math and smoothing to calculate total power (even more pronounced at lower cadences) and at pedal based power meters which tend to have the quickest response time since they are right at the dang foot.
So back to the original calibration or not issue - if you are using power match it doesn’t matter at all what power the trainer is transmitting. The adjustments will be based upon your power meter either way. If the trainer registers 455 watts, the power meter 305, and the target is 300 the application will just say reduce power by 5 watts and constantly fine tune to keep your power meter readings at the target number