I would consider it equal or very similar to a format which shares the dimension of the longest side.
e.g. a 6x6 or 6x7 format will be similar to the 24 x 65 format.
The depth of field with the Xpan will be the same When exposing a 24 x 36 frame or the 24 x 65 frame. It will only change if you enlarge the 35mm frame more than the wide frame.