Easiest way to rotate a discrete single-element object such as an
APXBOX at the sub-object level is to use Modify/ELEMENT/Rotate. No
need to select all the vertices and/or faces in the box. And yes, it
will indeed correctly rotate the local coordinates of the APXBOX,
which Modify/OBJECT/Rotate will not do (it keeps the local
coordinates aligned the way they were with respect to the world
coordinates).