Random thoughts.
I had a listen to one and found that it did make a perceivable distance, both with the mic and far from the kit. I personally did not care for it, and disliked the branding ascetics.
As an engineer, I know that any time air flows past a flat plane, there's turbulence, which manifests itself as distortion. Adding a flange to the ingress and egress reduces the turbulence. Adding a distance between the ingress and egress can change other attributes.
The kick port appears to address some of this, if only by accident. It's weight also dampens the resonant head and applies quite a bit of torque because the head supports the weight.
If I were going to sit down and pencil out a port which does what the kick port 'claims' to do, I would flange both sides, support it internally in the bass drum rather than torquing the reso, and make it telescopic so that the length was adjustable. I would make a highly elastic fitting where the outer flange contacted tone reso head to reduce the impedance and dampening.
And after all of that... it probably still wouldn't be a guaranteed improvement or produce a meaningful difference. Remember, a BD port is not like a subwoofer port. There's no 3DB gain because you're putting a hole in the resonator. Imagine porting a subwoofer through the speaker-cone. The best you can hope to accomplish is to reduce distortion and make the sound directional.