Germany is really struggling with exactly the problem you dismiss. It is relatively simple to take one isolated pocket and only draw from the grid when the batteries start to run low. If you can give the utility an hour's notice, they can start spooling up generators. Give them notice again when you are going to disconnect and they can orderly shut generation down.
Requiring the smooth two-way transfer of power is a more complicated problem to solve, even if it eliminates the bank of batteries. It also requires that the entire system be set up to handle distributed generation, whereas the Musk solution makes no such demand. In practical terms, this might make solar more viable in places where it is politically difficult to make infrastructure changes.