It was just an offhand number, there's already 17GW of storage in ERCOT's interconnection queue for the next few years, which is 40GWh - 70GWh. By 2035, the soonest we could expect to see a new nuclear reactor powering on, we will have many multiples of 70GWh. Not sure if TWh will every be needed for a grid that only peaks at 80GW. The cheapest solution will be a tradeoff between excess renewables capacity and storage, it will be interesting to see what the market picks for Texas.
70 GWh of battery storage would have kept the lights on for an extra 2 hours during this event - assuming the batteries themselves aren't affected by temperature. While battery storage might be nice to increase the capacity factor of a solar or wind farm it isn't going to make a difference in an event like this where a weather system moves in for a week.
The current grid took a looot longer than 2-4 years to build, and that 17GW/50GWh is just 2-4 years of replacement equipment at the very beginning of a transition. So I'm not sure why this amount of batteries needs to power the entire grid, or how that's a helpful or even interesting comparison.