He is just being polite and don't want to insult the buyer. There are no studies on frequency response showing that people prefer this over a neutral response, quite the contrary.
People buy poor speakers all the time. Often due to what they believe in and not actually proper AB tests. They "like" it only because of bias and money they have spent. In the long run, most will sell them and get a new speaker.
Seems like Børresen also are blatanly lying about their speakers. The graph below are their own measurement of the response and phase with the comment that "the speaker is extremely linear and with an equivalent flat phase response". They also comment that the response is unsmoothed.
View attachment 406927
A flat phase response is physical impossible to achieve with such a speaker design BTW.