It is all about phase (when the signals from the left and right reach your ears) which is easily manipulated when making the recording. If one system has a different width then one is preserving the original phase better than the other i.e the other is shifting it more than the other., and the shift will probably be different at different frequencies since speaker crossovers are the largest contributor to this shifting.
Steve Swallow - Deconstructed "Running in the Family" (available on Tidal and Qobuz) opening bass line sounds like he is sitting next to me. It is so far outside the speakers and so diffuse it is difficult to listen to for some reason. My speakers have a single cap in line with the tweeter, a single inductor in line with the woofer, and the mid-horns run full range so about as minimal a phase shift as possible for a speaker.
Steve Swallow - Deconstructed "Running in the Family" (available on Tidal and Qobuz) opening bass line sounds like he is sitting next to me. It is so far outside the speakers and so diffuse it is difficult to listen to for some reason. My speakers have a single cap in line with the tweeter, a single inductor in line with the woofer, and the mid-horns run full range so about as minimal a phase shift as possible for a speaker.