Indeed.
Thiel's requirements of passing a square wave / exhibiting a single, proper step response, etc. increase difficulty so much that most practitioners consider it impractical or even a fool's errand. We went for it despite the difficulties. We were young and idealistic, plus we wanted to make a mark and improve the art. Over the years, we invented improvements that managed the inherent problems.
The biggest problem/ limitation is dynamic range because each driver covers 7 octaves rather than 2 or 3. A driver acting outside its sweet spot has larger excursions, must dissipate more heat, enters break-up, etc. All those must be counter-acted with considerable difficulties. We began inventing new driver technologies withing the first several years.
It is also much harder to get smooth frequency response in a coherent system. Thiel's elaborate crossovers create complimentary circuits to correct driver anomalies that steeper slope filters would make less obvious. Also, we migrated to stiff diaphragms because their mis-behaviors are simpler, more predictable and therefore more manageable with circuitry. Those components introduce their own sonic degrades and add cost.
We addressed these issues as cost effectively as possible. Our performance per cost was extremely high. As manufacturing director and later consultant to other manufacturers, I know that our output/cost was a multiple of average and our margins were a fraction of average. We tried harder.
Thiel's results were often less than best in some respects, but generally first-rate if one values over-all high performance on all fronts. Our speakers addressed everything quite thoroughly rather than a few things brilliantly. We believe our products supported a more musically authentic experience than conventional approaches.
I can say that Jim / we might not have gone there if we had known how hard it would be. I suspect that hind-sight and insight would have led us to the later-stage insight that we used in home theater products. We could maintain respectable phase coherence and proper time alignment while considerably reducing difficulty with the fudge of keeping first order slopes for an octave on each side of the crosspoint and then migrating to second order symmetrical slopes beyond that. Out of band excursion and erratic behavior is greatly minimized while keeping the critical advantages of single step response and coincident time arrival. But you can't solve the puzzle until you know enough to solve it.
Most brands didn't and still don't even try what we we did. I'm glad we did.