Would they image? Possibly or we would not have stereo, would we? OTOH, that is with slightly different signals. If you compare a mono signal over the pair with a mono signal over a single centered driver, you can hear the difference in terms of image stability with respect to head movement.
As for the ubiquity of MTM centers, that is a model supported by its visual, rather than its sonic, impressions for accomodation to those with the common space constraints. The only good centers have vertically stacked tweeters and mid-ranges. A standard speaker configuration is even better.
Kal