Yeah that vid is a bit sad really, theres a few cars out there that do that if you keep them on the rev limiter ( ignition cut type )
Two stage / Two step , whatever you wana call it is useful for getting off the mark in boost, but without having redline like revs.
The " bang-bang " is just a side effect of that.
The real " bang-bang " aka Anti Lag is useful when you dont have your foot on the gas, on a turbo car .... keeps the turbo spooled...so when you do plant your foot back on the gas, you have boost

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Take a peak at this video
http://www.youtube.com/watch?v=puGCda4ThvU