Most line source speakers exhibit an extreme narrowing of the horizontal dispersion pattern in the higher frequencies. The ribbon Davidson is using has this characteristic at high frequencies, and does not require a downward sloping frequency response to sound natural. It is a matter of taste which perspective you prefer. Apart from the differences between a floor to ceiling dipole line source and all other designs, many loudspeakers are built to have a highly idiosyncratic frequency response with one or more areas of boost or cut. This designed-in voicing colors the sound of every recording played.
Some people become very attached to a specific coloration.
Finally, most loudspeakers are designed with a hump in their frequency response of 3 to 12 db in the range from 40 to 90 hz. Regrettably, many audiophiles, who would never consider using an electronic bass boast are addicted to speakers with a designed in bass hump. Mama, please don't let your kids grow up to be Pangas.