There are some important differences. For one, those are using bespoke new batteries, not used car batteries. For another, the battery storage is not concentrated, so much lower risk of fires spreading from battery to battery (which you've ignored).

For a third, if a battery fails, it's most likely going to be the house whose battery has failed that loses power if the grid was at its limit, it won't be a whole neighborhood, nor some industrial plant.

Finally, I would be quite surprised if there is any significant power grid where any industrial consumer would be at a risk of losing power even if all community batteries were to be unplugged from the network (ignoring the effects of a sudden surge, like in the oven example, of course).