On one of the in-car videos, of one of the cars dying abruptly, I could hear the turbo/energy retension system winding down. It sounded like a huge shop-vac being turned off.
I realized, with the turbo being both driven, and driving (electrically) these cars reminded me of a famous hillclimb car that used a small turbine engine to maintain full boost at all times.
While the F1 engines are transitioning from off, to On throttle, the huge turbo is being driven by an electric motor so boost is available anytime/no lag.
The car in this vid kind of ran with the same concept.
These are tiny little engines (1.6 liters) and I suspect the turbos actually have more displacement than the engines.
Crazy technology. Amazing that they make it all work, with the braking/recharging balance