Alison was going for wide and uniform dispersion and getting the woofers as close to the floor and wall as he could with the angled fronts of the One and Two. That made in room response more predictable, particularly since the speakers were essentially unusable in any location other than the one intended, against the wall, away from the corners.
Other angled driver systems may be less rigorously thought out, even though some sound excellent (and many not).
To respond to the OP's original question, there does not seem to be any consensus about the ideal number of drivers. A strong argument can be made for one being the correct answer, since it creates a point source, but translating that into a full range speaker is a very great challenge, even if whizzer cone or coaxial drivers are accepted as meeting the the definition. The more drivers used, the more comb filtering there is, and if the drivers cover different frequency ranges, they may interfere less, but phase relationships and the effects of crossovers become issues. The farther away you are from the speakers, the less some of these problems seem to matter, though, of course, getting far away requires the speakers to be able to produce more volume to fill a large room, and that is another issue.
