Dynaudio woofers have a smooth roll-off free of resonance peaks, as watchnerd has already said, which makes it possible to use such flat filters. Flat filters make a very wide transition region where both woofer and tweeter play in parallel.
The directivity of the woofer increases with frequency, especially above ~2 kHz. Then, a tweeter which is mounted in a 7" baffle without waveguide or strongly rounded edges has a very wide dispersion around 3 kHz (due to reflections at the baffle edges). The directivity of the tweeter starts to increase above ~6 kHz.
Now, those factors in combination with the high crossover frequency around ~4 kHz and the flat/smooth crossover filter make the woofer's narrow dispersion to compensate the tweeter's wide dispersion and vice versa. This gives a controlled horizontal directivity in the critical frequency range. As I have mentioned in my last post, all this is at the expense of vertical directivity and intermodulation distortion. That's why I called this a dirty trick.
But I admire how good this trick works and how effective it is: A classic speaker design with 2-order filters and a crossover frequency of 2 kHz would feature an increasing directivity until 2 kHz, whereas it becomes wide at 3 kHz and increases again above 5...6 kHz. To overcome this effect and to provide a smoothly increasing directivity vs frequency is why so many speakers with controlled directivity have waveguides. Also, a waveguide and high-order analog/passive filters (which is not the case here, but in other Dynaudio designs) would increase cost. So, all you need is a woofer with smooth roll-off.