This avoids reducing high-order geometry to linear when no field is present.
$ $PETSC_ARCH/tests/dm/impls/plex/tests/ex33 -dm_plex_simplex 0 -dm_plex_box_faces 1,1 -mesh_transform annulus -dm_coord_space 0 -dm_coord_petscspace_degree 3 -dm_refine 1 -dm_view cgns:test.cgns