"No, that’s not the way electrical grids work.
Firstly, grids dont discriminate between “car” and “your employers computer system”. If demand exceeds supply instantaneously by 30% that’s a general brownout where most electrical goods don’t work."
No - but it can be the way car chargers work.
We basically have large computers which keep themselves charged and, as a side effect, allow personal transport.
The coordination is possible without resorting to changing the grid hugely - you have predictable (and potentially controllable) demand, which can also act as a balancing mechanism for the vast majority of vehicles.
Of course since new vehicles last many years before being replaced it will take a while for all those cars to be electric - at which point the early vehicle batteries will have been pulled from vehicles because the "only" have 85% of their capacity - which is fine, that battery will service household UPS or grid level storage for years to come - giving even more controllable demand/balancing.
Just because we used to use horses to travel long distances doesn't mean that cars are obviously useless and never going to work...