Ok, but turn-on time of your crowbar is about 1µsec, while the transzorb turns on in about 1nsec!
OK, maybe not a good way to handle screwdrivers, but for protection of the output of a switcher it has worked extremely well for me. Before installing the crowbar, all electronics became unusable (shorted/open) when the switcher popped, with the crowbar all electronics survive.

Erik