I think what David is asking is it CoreXY kinematics or Cartsesian with two motors on each axis. To clarify, on a CoreXY, both motors contribute to motion in both the X and the Y directions. If only one motor turns then the gantry moves at 45 degrees to both axes. It sounds like your dual motors only drive one axis at a time. If that is the case, then it's not CoreXY. Maybe a picture of your printer would help.
Edit I was typing while you were - pleas ignore the above.