I think we're talking about using ice as energy storage: create ice during a time when the supply of electricity exceeds demand, and then use that ice for cooling (AC) at a later time.

No, or at least not without more steps and automation. WAY back before refrigeration, cooling was done with blocks of ice harvested in winter and stored for the year. Expensive is a word for it.

What's being talked about here is thermal energy storage. Ice is created overnight (ok, like a refrigerator), but then during the daytime used to supplement or replace the refrigeration cycle of the compressor to reduce electric load while still providing cooling. I can't quickly find an article (edit: found a 2016 paper, see comments about Boothbay on page page 3-4: https://www.aceee.org/files/proceedings/2016/data/papers/3_2...), but it's memorable to me that an island in Maine installed these systems instead of spending more on replacing the distribution line to the island the handle the peak daytime cooling load.