Surprising amount of horizontal error for a horn loaded coax three way - not that it's very much, but still.
This is very much speculation, but if you look at the mid driver, you'll see that it is very slopped inwards for a driver, I assume that is to ensure that the dome driver is sufficiently loaded to provide high enough SPL. The mid driver is shaped unusually, that also has an impact on its radiation pattern, even inside the waveguide/horn structure.If only it was a little deeper....
Sidenote: I want Erin to get one of these to see how it compares to the JBL M2. Price and SPL capabilities are quite similar with a slight advantage to JBL on paper.