Yes, things like this make comparisons based simply on driver cost not very helpful,
"The holes are another part of the design. You may have noticed that as you drive loudspeakers harder and harder, they get “bright” and eventually harsh sounding. Harmonic distortion starts an octave above the real signal and extends upwards by 2,3,4,5 etc times the input frequency.
While that brightness may not be objectionable, the object here is to be a faithful reproducer and one thing that means the spectral balance should not change with level if possible.
The trapped air volume under the cone and the small holes, form an acoustical 2nd order low pass filter, like an electrical filter but in air. The object being that the harmonic distortion the drivers invariably produce, will be attenuated and not enter the horn. The effect does limit the bandwidth and that is the object of it. The idea is you DO NOT want sound the driver produces on it’s own (not part of the input signal) which is always above the electrical crossover and the short obstruction does not affect the horns radiation resistance.