I'd suggest that possibly the disagreement on what's been referred to as point #4 is in part at least semantics. One purpose of a center speaker arrangement is to localize the center channel material as precisely as possible to the center of the screen(ideally to an area as small as the mouth of the actor speaking). A different objective is that the speaker or speakers should have as wide and smooth a horizontal dispersion as possible, both for listeners not in the center and for the reflections from the side walls, regardless of listener positioning. So, the center channel material should be both highly localized and widely dispersed, and there's no inconsistency between these objectives.
