Hi jt,
You got it. That indeed is another virtue of using a center, to avoid the "hole-in-the-middle" effect when the main speakers are widely spaced, and to minimize the collapse of the stereo image when listening off-axis to the left or right.
In the 1930s, Bell Telephone acoustical/electrical engineers experimenting with multi-channel live transmission (over telephone cables) of concerts by the Philadelphia Orchestra concluded that a "minimum" of three channels--left, center, and right--were necessary to realistically portray the stereo soundstage of the orchestra.
Recording technology at the time was not up to the task (only mono was possible), but engineers even then recognized the serious limitations of mono or two channels (stereo).
Regards,
