[MrForbes]

"At the start of, and during, the MATCH the ROBOT shall fit within the
orthogonal dimensions listed below: "

That means that the dimensions are orthognal, the 28" x 38" x 60" space that the robot must fit into, is a right rectangular prism. That does not necessarily imply that the robot itself must be orthognal.

Of course you are encouraged to ask on the official Q&A to make sure! Perhaps you could ask if robot shapes other than rectangles are allowed.