When you invest a ton of time into sorting out a metric to quantify the results you are after, it would only make sense that speakers produced from the company following the definition of the metric might align rather well with it. Of course the little JBL LSR 305 is rather accurate by that measure as well. Realize the host also is a big proponent and seller of the Revel and JBL Synthesis products, and has gotten into more than his share of the kool-aid.
To be fair, the metrics they defined make for a very good indicator with regards to frequency response, power response, and overall directivity (on vs off axis performance). Speakers without huge irregularities in the 3+ plots of their overall behavior will be much easier to set up in real listening spaces. If anyone followed the link to the later pages of the thread, Floyd Toole also added that elimination of resonances is of top priority, and reducing distortion is the goal, but simple numeric reduction of THD doesn't always correlate to sonic improvement. His acknowledgement of distortion came in this statement
in the linked thread: "the only meaningful number is zero. The closer to zero the better, but the number itself is not a reliable indicator of audibility." I would argue we know a lot more about what is and is not audible than he is acknowledging. Wolfgang Klippel has moved forward our understanding and quantification of driver non-linearity as much as Harman's loudspeaker metric has for complete speaker, spectral balance preference.
As a speaker designer I see the "spin-o-rama" and overall metric as only one part of many important qualities in a speaker. Remember Floyd Toole and his team are first researchers, not product designers. They are searching for what they can prove statistically. Anyone with a solid background in professional acoustics should find none of their results to be startling nor revolutionary. The hi-fi world does have a long history of only caring about the forward 30-60 degree cone of sound, often to its own detriment. Their research provides very good affirmation of why the full sphere of sound should be considered in a speaker's design. I'll be the first to get into a heated debate with the absurd concept that you need a million dollar anechoic chamber to be able to design a speaker that performs well in these regards. You do need to understand core acoustic concepts along with finer details of acoustic measurement techniques.
IMO, the more interesting bit will be to hear listener feedback on the subjective differences of two speakers that have significantly different directivity, where the wide horn of the M2 greatly reduces the energy sprayed 90 deg from the speaker's axis and especially in the rear hemisphere. I've set up a few home theaters with M2's, and they are a very capable speaker. They might not fit everyone's preferences, but they are very well designed and executed.