This boils down to "There are lots of EV batteries, we can use them as storage!". It seems to ignore practical issues:

People drive during the day, and charge at night. So you could use EVs as a buffer during the night, but they still need to be charged. So EVs are still going to be a net energy consumer during the night, when you need the storage the most (no solar production).

I think the best course of action is to load shift charging of EVs and use it as "storage" in that way. Its an easy load to shed when needed, and an easy load to ramp up when renewables are plenty.