No, he makes different assumptions. His assumption was not all electric right now in the 2020s! Different assumptions, different conclusions. Simple when you understand
"Not all electric right now in the 2020s" isn't an assumption, it is a fact.
They aren't even due to stop manufacturing "pure" petrol & diesel cars until 2030, and it will be a number of years after that before almost all the cars on the road are purely electric.
If you are saying we don't have the generating capacity right now to power a completely electric population of cars, then that is also a fact. But a fairly irrelevant one since there is zero possibility of having a completely eclectic population of cars in the next 10 years.
Whether we can ramp up generation sufficiently by the time it is needed is an important question. But few of us are really in a position of sufficient knowledge to be able to give a definitive answer on that.