One of the rare times that I do this, BUTTTT, the article could actually be correct.
Not saying that they are or aren't. But they could be. It depends on the limiting factor. Is the limiting factor total energy? Or energy rate?
In an electrical grid, the rate of flow is CRITICAL. If you can produce 6 gigawatts (GW), but the grid is demanding more than 6 GW, then your frequency will start to drop from 60 Hz. The supply rate (in GW) MUST be able to keep up with demand rate in GW in order for stuff to generally work.
Back to the article, batteries could be part of a solution to provide a specific RATE of energy. And their ability to do it for how long is less relevant. ESPECIALLY since if your links can't keep up with 60 Hz due to too much demand, then you'll get out of sync with the rest of the grid and have to pop off, which only escalates all of your issues.