This is grid following, very effective for small scale generation. It does not work for large scale generation though when the grid is relying on that voltage and frequency from the utility scale renewable generation ("grid forming"). When those large generators exceed their ride through tolerance, batteries step in to hold voltage and frequency up until the transient event ends or dispatchable generators called upon spin up (currently fossil gas primarily, but also nuclear if there is headroom to increase output). Thermal generators can take minutes to provide this support (called upon, fuel intake increased, spinning metal spins faster), batteries respond within 250-500ms.

Tesla’s Megapack system at the Hornsdale Power Reserve in Australia was the first example of this being proven out at scale in prod. Batteries everywhere, as quickly as possible.