pscan.uk

These features are reverse engineered from a factory MG Rover T4 diagnostic tool.
The answer to the question "what does the feature do?" is, the same as a T4.
I can't tell you what is going on in the inner workings of the ECU because I don't know.

I can only guess, and here is my guess:-

Normally ECUs will "learn" the input signals from sensors in order to compute out unknowns such as the tolerances in the sensor signals, or other things outside of the manufacturers control such as fuel quality. Essentially if they have two out or three sensors saying the same thing and the third is 5% out, then the ECU will "learn" that the third one is 5% out and calculate everything on that basis.

There will be a limit on this adaptability. If a sensor is 50% out then that means that the sensor has gone bad or something else has failed and then the ECU will enter an error state and log a fault code.

I enterpret resetting adaptations as meaning that the ECU forgets all of the tolerances that it learned and starts again.

If the learning algorithm is perfect then it wouldn't matter but maybe it isn't. Maybe there are corner cases.

My guess is that the intended use is that if a technician changes something, like fitting a new sensor, then reset adaptations makes the ECU relearn from the new situation so that it gets there quicker.