But how do people realistically prep for this? Not a historian, but in my understanding, when major metropolitan areas devolved, people had to spread out significantly in order to restart the agrarian lifestyle that could sustain them without the complicated "modern" economy. This isn't feasible for cities like New York or Tokyo, and those people are not able to purchase a homestead and stock it with these things ahead of time for a hypothetical situation.
It feels like you're suggesting prepping for a Shit Hits the Fan type scenario, which the OP post explicitly says is unreasonable. It postulates a world where most people would starve because growing plants to survive through a year is extremely difficult if you don't have any experience doing it, assuming you have enough land time and other resources to even do it properly. And I guess I just doubt that a box of seeds and a willingness to share your garden would see you through the year. You would need a whole lot of luck.
It feels like you're suggesting prepping for a Shit Hits the Fan type scenario, which the OP post explicitly says is unreasonable. It postulates a world where most people would starve because growing plants to survive through a year is extremely difficult if you don't have any experience doing it, assuming you have enough land time and other resources to even do it properly. And I guess I just doubt that a box of seeds and a willingness to share your garden would see you through the year. You would need a whole lot of luck.