As usual, further research brings forth answers. It seems a big part of toeing in speakers is that it removes the room somewhat from the sound. As speakers are angled inward, early reflections from the side walls are reduced. This makes sense. Of course the tweeter design itself plays a role too, and I値l need to read further about that.
Not really in the same vein, but more toe-in makes for better off-axis listening in my living room. The angle reduces output of the speaker closest to me, and the farther one is pointing more toward me.
Thanks and back to your regularly scheduled listening...