I would hope that the ones cops use are bolted down to the center console, not held in place only by the closeness of the PVC diameter to that of the cup holder. Unless I'm missing something, nowhere does he indicate that the piping is held down with anything (glue, bolts, etc.).
What happens in an accident? Or a hard bounce? If drinks can bounce out of their cupholders, how much easier would it be for an 8lb. laptop (plus plywood)?