There will be some EVs in that scenario. Enough to tide things over. But in a world with only one option, anything that blocks that one option will destroy the whole car industry.
But oil blockades won't stop the production of new ICE cars. A battery-related blockage will stop new car production. That would be a big crisis for automakers.
Again, the point is to not ban any kind of car as a redundancy. You've created an elaborate narrative of what you suppose your opponent is claiming. It is time to stop.
That means people could still drive EVs even if there is an embargo because we'll always have power.