I think you're oversimplifying here. A good 3-way, be it a monitor or tower, allows you to choose a woofer large enough to do serious bass, and still maintain broad dispersion in the upper midrange and lower treble because those areas can be handled by a midrange driver better suited for the job than a large woofer. If you choose the right drivers and know what you're doing, the sound can still be seamless despite two crossover regions. That said, I would take a well-executed 2-way to a so-so 3 way any day.
Since he mentioned bookshelf speakers I was assuming he meant speakers that could at least be placed in a bookshelf. Yes, large diameter woofers do increase the low end reach and power handling do make a case for a three way speaker.
The point I do want to emphasize though is that the route to better speakers is though wide band width drivers. In you design that mid range is a wide band width bend driver by design.
I think at long last Ted Jordan will get his due. 60 years ago he pointed this out.
I think of all his drivers this was the best of them, his first. Although for a lot of reasons quite a few people ended up having a hand in it including myself.
It has a unique suspension which gives it a good xmax to this 4"cone and a good bass response. It is a true full range driver and appeared in 1959 first, although the MK 1 had a half life of about 20 min.
At our Eagan home in our secondary listening room I installed this pair using only one of these full range drivers a side. It is a small room.
I have really enjoyed listening to them. They create a wonderful sound field and sound nothing like the usual typical full range offerings. You would never guess you were listening to two single 4" drivers.
This has made me realize it is now time to work again with drivers that can handle if not all the audible spectrum but most of it.
I'm convinced Ted was and is right, reproduction is not just about a flat frequency response, though that is a prerequisite, but also about keeping harmonics properly tied to their fundamental frequencies as far as possible.
Now 60 years on it is a scandal that we have so few really wide band drivers. I think things are about to change though with some very competent driver engineers becoming engaged in this task again.
I'm convinced that one of the major reasons people are pleased with your design is because of the use of that very wide band midrange driver.