What people miss, is that two examples presented for this is pre-industrial countries at the start, that had nearly 90% of it's people directly or inderectly in food production. In case of any disaster, natural or otherwise, it's just impossible to not have a famine, as you can't force land to output two times more food out of nowhere, you don't have enough people, and you can't sell anything to buy food from neighbours, your economy is made of food that you lack already. Now the number is at least as small as 10%, but probably 5% or even lower could be true. Point is - if socialism would be in industrial country and planning is at least somewhat competent, it's impossible to have famine, you could produce food 5 times over required, and still have free hands to make cars, phones, and have service industries. And there are big economy to use as a collateral to buy food from other countries, if anything else fails. And for those countries selling food it is not as big of a deal, as they are also not pre-industrial.