I don't think you really got what I wrote, or maybe I'm misunderstanding you
The amount you can fit in your stomach per day doesn't change much in real life. If you're eating under your nutritional needs, even if you're physically filling your belly you'd still accumulate "starvation" as the game has. Trying to replicate this in game would probably make the system more obtuse than it already is. The simplified system makes being under nutritional requirement a real pain, which makes it worthwhile to starve rather than to eat bad foods from a player's convenience point of view.
In URW it already works like this, as I mentioned in my previous reply.
The HUNGER meter limits in how many lb of food you can ingest in a certain amount of time. It has a few other effects, eg it can wake you up at night, and the hunger meter rises faster when you are Starving rather than when you are Abundant. But mostly it's the limiting factor.
I don't get your last sentence: how is it worthwhile to starve rather than eat bad foods? It's actually the opposite. It's better to eat spoiled foods than starve in URW - you will be more hungry but retain some of the nutrition. I never need it though, so I'd have to test this.
I think the big reason that confused my nooby self is that there's no real good foods in the early months other than meat. Starting in spring or summer, your options are all not really worth eating with how the game represents nutrition (basically since we ignore vitamins). This gets compounded when villagers start selling turnips, which are a food basically in game for immersion and no real mechanical reason. It makes sense people like myself throw their hands up when even village vegetables suck. Faced with those stumbling blocks, I can see why I got frustrated and so do others even though good plant foods do exist in some instances.
Villages should have plenty of other veggies. Turnip is really the worst.. there are plants that can give you enough nutrition to keep you going. Barley, rye, nettle, hemp, broad beans, peas, and also the great lake reed root that can be found around. Some can be eaten straight, some can be ground into flour and then made into flatbread, some must be threshed to get something useful out of them, and the products can be used either as vegetables or as seasoning in the cooking recipes.
The turnip is a great bait for herbivores, from the rabbit to the elk. So I always get some for traps. I also usually buy turnip seeds and plant them, just a few, and then thresh the grown turnips to get new baits, and turnip seeds to be used in recipes as seasoning.
There's also the issue that our cooking options don't really help us here. Soups make things less calorie dense, but because filling our hunger bar depends basically on how calorie dense our food is it's counterproductive.
Just to make sure it's clear, I'll reiterate. It's not the "hunger" you are filling, but your calorie storage. I believe in URW the maximum you can accumulate is 5000 kcal, while Abundant appears when you are at about 3500 kcal. If you eat anything when you are at the maximum, you are wasting food. So I try not to eat when "Abundant", but only at the level below.
Now, it's true that soups are really not that helpful unless you have very little stuff to eat. I believe stews, instead, are better than roasted meat for example, because the stew lasts longer and should have less water content, so it should have higher nutritional density. I'd need to double check this though.
I think if our cooking options allowed us to make more calorie dense foods out of our low density vegetables it might help, but we'd quickly hit another roadblock of it being hilariously difficult to gather enough of those foods to actually make something out of them.
Some of the plants I mentioned before are very caloric. If you don't want to use meat, you should to subsist on high-nutritional vegetables. Barley flour porridge with hemp seeds is crazy nutritious and my no-meat preferred option, but I've built a log cabin substisting only on raw lake reed roots and the occasional trapped bird.
Nettle is great: seeds and leaves are nutrition enough to make better stews/soups, and the leaves have also great medicinal use. I try to always cultivate a bit of nettle (I have a mod that allows me to make nettle clothing, and cords from nettle, so that's how I use it too)
Some berries are also worthwhile to eat, most notably Cloudberries but also a few others are not too bad.
You can see a lot of info here:
https://www.unrealworld.fi/wiki/index.php?title=Plants