Sure it does. The goal is keep the farmland available and productive along with keeping agricultural infrastructure. The USA helped win WW2 because our car factory lines were retooled to make war machines.
Demand for war materials goes up in a war, but the population and thus food demand isn’t going to drastically spike.
There’s a reasonable argument for having a food stockpile in case of emergencies, but extra farmland is harder to justify.
The demand won't spike, but the need to switch to local production necessitates some way to locally produce.
That’s limited by the country’s basic requirements not the total amount of farmland available. People may prefer wine and beef in surplus resulting in an obesity epidemic, but that’s not required here. You don’t want 350 lb soldiers or recruits.
In the case of the US, we turned much of the richest farmland into subdivisions. The breadbasket of the nation is powered by an aquifer that will be depleted in my kids lifetime. Most of our green goods come from the deserts of California and Arizona, and won’t exist if the Colorado River water system breaks down.
That aquifer is being depleted because of farm subsidies not in spite of them.
The US’s domestic demand for food is vastly below the actual production, exports and biofuels need not be maintained in a war.
You are going to stockpile years worth of food for an entire country?
No, if you expect farmland to produce 0 food then having extra farmland is pointless. 0 * 2 X = 0 * X = 0.
The point of extra farmland is to make up for some expected shortfall, but you’re better off stockpiling food during productive periods than have reserve capacity for use when something else is going wrong.
PS: It is common to have quite large stockpiles of food. Many crops come in once a year and then get used up over that year. But that assumes a 1:1 match between production and consumption, a little extra production = quite a large surplus in a year.