Yeah, more or less. Your inaccuracies will be tripled, maybe check that it actually does shunt at the absolute max Vgs. Otherwise a nominal 5V TVS which actually trips at 8V * 3V = 24V Vgs and a dead mosfet. But the reason that
By contrast, things like gas discharge tubes and trisils cannot be used in series, because the V/I curve is discontinuous so you might end up with weird halfway states. But TVSs just have a nice monotonic VI curve; and putting them in series just triples the voltages.