Sloped baffle

It's not crystal clear to me that Hales really said that, from how it is written. It does not appear to be a quote.

But it would be so very refreshing to hear that honesty from a designer.

I believe it. Hales uses fourth order crossover. It is of course not time coincident as one can see from the step response. You could speculate that part of the intent is to visually differentiate the transcendence from the revelation line, which it does.

Pay attention to those manufacturers that have intentionally run the mid driver in reverse phase to the tweeter and woofer. This indicates a bandaid approach that will ALWAYS compromise timbre, the accuracy of which is dependent on time and phase coherence.

Reversing the polarity of a mid in a 3-way or a tweeter in a 2-way is just a result of correcting for the phase shift of the crossover. The exception being 4th order. It's about getting the drivers to sum correctly. If they were 180 degrees out of phase, they cancel around the crossover point. In fact, one of the best ways to confirm the drivers are in phase is measuring the reverse null.

Now, if you want to talk about absolute phase and the half a millisecond @ 2000 Hz between cycles and whether that's audible, that's a different story. I don't know the audibility threshold up there but down around 100 Hz, it's around 30 milliseconds and several cycles for our ears to respond. Less for the trailing edge.

http://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2

That's bound to be misunderstood. Related articles in links.

The 30 milliseconds I mentioned previously came from a U-tubed Earl Geddes seminar on multiple subwoofers in a small room.