proper rollcage tubing is CDS, Cold Drawn Seamless tube.
exhaust tubing, and the stuff in that car, is not, you can clearly see the seams in the first picture. its just rolled plate welded up.
i can just imagine the dash bar for example, kinking in the middle when someone runs into the door, splitting at the weld, and stabbing someone in the guts
not to mention the gauge of the steel.