Triangles quite low level internal data. mesh could output also 4 point polygons on occasion. of course we can add an parameter to mesh to let pythonscad combine the faces as mush as possible(sub-faces are coplanar) and you would actually get 6 squares for a dice), even polygon would accept faces with n points as input.

however, openscad does not have an internal B-REP kernel and you would have to rewrite the program to change that.