I agree that going fully electric probably makes more sense, but some people like the engine noise and they want to be able to drive a car anywhere without being worried about the EV range.
This system would be perfect for a tuner who tuned his/her car to the max and could add this for even more power. You could make a 911 Turbo S that drives like a 918 for a fraction of a price.
Here is a clip of the test drive:
https://www.youtube.com/watch?v=OKSCUre0-Co