roulis
A european manufactor test pilot is not independant to rate their own aircrafts' qualities.
But they routinely do so in the flight test development programmes to ensure that there are no problems and to sort them out if necessary. Before any aircraft gets certification its handling qualities are checked again independently by one or more of the
airworthiness authorities' test pilots. Whether or not they use the Cooper scale is a matter of choice for them really - you don't have to give an aircraft a numerical rating to say whether it is pleasant and safe to fly - subjective judgements are just as valid and in practice a Cooper rating is nothing but a numerical statement of a subjective judgement. APA were just making waves.....
A question about Harper-Cooper rating : is it done with and without Yaw Damper on ?
Whatever the test pilot is trying to assess. The Cooper scale is just a numerical scale which can conveniently be used to methodically categorise the relative acceptability of various configurations.