You go back to the descriptive bit, rather than looking at how I directly addressed this. Fine.
The dam is breaking, and the adventure is about that. You are worried about the French drains around individual homes. Continued focus on how individuals manage to not have their basements flooded will not deal with the leaking dam.
Is the adventure about how people manage to survive when it is cold and dark, or about how to make it warm and light again? If the latter, the former is probably not really relevant. You may be curious, but it isn't necessary to know to get the issues dealt with.
I think your last paragraph shows the point you are arguing from the best, but also puts a bit of a stark contrast on the way this issue works. For me at least.
Is the adventure about how people managed to survive or is it about returning things to the status quo? Well, like you said the adventure is about returning things to the status quo, and that can mean that "how are they all still alive anyways" matters less...
Except, this ignores the aspect of tone I think. Because "how did they survive" plays into many different parts of potential narrative. The Players are going to react differently to the towns if they have survived through cooperation and pulling upon decades of prepared food stores as opposed to those who have survived by human sacrifice to the Maiden.
Depending on the elements you want to pull out and confront your players with, different solutions and desperate gambles will have different impacts. The players may be appalled at the sacrifices, but the townsfolk push back, pointing out that they have no choice, there is no other way, and they have made it as fair as possible, doing legitimate random lots to decide who dies. It raises questions for the players, how far do you go to survive? Is it better to sacrifice a few to ensure long-term survival of the group, or to hold to morals and condemn everyone to death?
If you go the route of rations and stores, you've highlighted resilience and planning. These people survived something that couldn't be survived, they had prepared and are toughing it out. Even as the food runs low, they aren't bowing, they aren't letting fear rule them. They are seeking other solutions. Maybe they do try and set up trade caravans with outside groups like the Dwarves. Maybe they did that early, and part of the story is the question of how much you can expect your neighbors to give, and when you have to stop giving and take care of your own?
Maybe the Druids in the area were supporting everything that first year, and as the second year drug on, they needed more and more of their power to keep the natural world from collapsing, and abandoned the towns. Maybe the players confront them about it, or maybe a player is a druid, and those druids point out that nature can't migrate south. But the people of the Ten Towns could. The druids are protecting the natural world, which is their idealogy, and shrugging and saying that if the people are too stubborn to leave an area they cannot survive, then Nature will take its due.
And now I'm picturing a version of this book with a sidebar that lists some of these things out. Maybe they didn't want to focus on these aspects, maybe they just wanted to tell the story of the great heroes who saved the day and brought back summer. But for me, heroes exist
within conflict. Being the good guy who does the right thing and beats the bad guy who was doing the wrong thing is fine, but adding those hiccups, those challenges where you have to ask "what would I have done, in that situation?" draws us in deeper. It makes the world feel bigger.
Maybe they wanted to leave it ambigious, so that the DMs and the players could decide what the story they wanted to deal with was. If they wanted something more traditionally mythical, something darker, something more about grit and determination, they are free to alter it. But, if that was their intent, I'd have liked them to state that, to give one of those multiple choice sidebars that says "hey, we didn't answer this question on purpose, but here are some ideas to get you thinking in case you want to answer it."
It think it would have made for a more powerful story in the product.
