The compatibility rating is similar to car analysis based on its ground clearance - on which road the car will move optimal without evaluating the class of the car.
The algorithm takes into account the sensitivity parameters of the headphones, the power parameters of the source and the use case: at home, at the studio, on the street, in the subway, etc.
Automatic selection is made only for headphones with measured sensitivity and resistance and amplifiers with definite equivalent power classes.