Is the speaker the one in the photograph? If it is it looks like a one cavity box. If it is one single cavity, then the drivers have to move in and out together, as otherwise there would be no restraint on cone movement.
I suspect the speaker is actually a bi-pole. You can check it with a battery.
In order to have both sides out of phase a true dipole, then the speaker has to be planar like electrostatics or Magnepans, or the drivers have to be in separate enclosures. If the speakers are truly out of phase, phase won't matter.
Usually surround di-poles have one monople bass speaker and the tweeters out of phase facing in opposite directions. Often they have a phase inverting switch to one driver, so they can function either way.