Side venting reminds me of the TAD CR1. It seems Sony has chosen the triple-tweeter array as their hill to die on. Problem is that in their previous, non-coaxial implementations (SS-NAxES series), it has even more dismal vertical dispersion than the typical cone-and-dome. So it makes sense to place the array in front of the woofer as the next step. I dig how adventurous it is and the design choices are (vaguely) rationally defensible. But yes, unless it has a larger mid like the Geithain such that it can be low-passed at a low frequency, I can't see how diffraction would not be an issue in the Sony.
If anything, Sony hasn't gone far enough with their array before placing it coaxially. Add a pair of midwoofers per side and it could have made a compact Horbach-Keele array - now that is something that is long overdue on the market (only design out is the Lexicon SL-1). No need for a finicky coaxial configuration.