It reminds me a bit of the game Oxygen Not Included where early food storage techniques involve keeping it stored in an area saturated with CO2 to reduce the rate at which it rots before you have access to refrigeration.
Technically food in a cold enough freezer will never get uneatable. It is indeed flash frozen to preserve its texture. The issue is that quality tends to get down with time due to water sublimation.
More practically, while sublimation hurts "quality", it does not harm the nutritional value of the food, so does not seem like that big of a deal in the context of famine policy.
For rice it is even less of an issue, because rice is routinly stored dry and rehydrated when cooked.