That's old school. I haven't even heard mention of a turbo setup like that in a long time. It's about as impractical as the supercharger/turbo combination I saw like, 10 years ago. It's possible, but doesn't really gain much. The stock VF52 won't produce 360 wheel HP on pump gas, not even close. It sounds like this guys has been standing around in parking lots talking to people who almost know what they're talking about, and then he spurts out the stuff he thinks will sound cool. That's my opinion, but whatever. I don't even think that 360 crank hp is a realistic figure even if he has a protune and TBE.
The problem with the twin-turbo setup is that the smaller turbo ends up being a block for the larger turbo, and might reduce lag, but also limits the larger turbo's potential. It's not as efficient as the kid makes it sound.
It is realistic that he's pushing 21psi of boost, as the VF52 can do it, just not hold it to redline. It'll taper down to 15-16 at redline.