John Atkinson knows how to measure a dipole...but I agree an average Joe would struggle to get the best possible measurement just like they would struggle to get the room and placement just right for that tiny sweet spot...reviewer gatekeeping is pretty severe with family owned hi-fi brands & really anything high end like Wilson/Magico...it's smart business.
Magnepan measures poorly due to things like phase cancellation and a first order filter...it appears some Eminent speakers do the same and the top model uses DSP for some frequencies...but higher frequency beaming with planar designs can't be fixed.
There are people that rip out the Magnepan filter & replace it with a DSP crossover to presumably level the response and time align the tweeter and midrange....to great satisfaction based on self-reporting....but to each their own.
This is not to say that one cannot love a speaker that has a highly uneven frequency response and ringing. Zu Audio would not exist if people didn't like what it did...including it's editorialization of the response and masking other frequencies.
Regarding Corey Greenberg, he did note a lack of coherence between the mid and bass panel. Steve Guttenberg noted the same. However, Steve Guttenberg noted an improvement in coherence with the DSP version...not surprising....but then he did mention he didn't like how the DSP changed the sound so he turned DSP off...so who knows...I have heard DSP sound terrible and I have heard DSP that is transparent...all about implementation and the technology used of course.