I don't like requiring food to rest because it won't matter in the end.
I do not believe that they would put a limited amount of food on the act, and if the player consumes everything, start over.
This is definitely a bad game design.
So there are two options either larian will put absurd amounts of food in the game or they will respawn at the traders. The first option is forcing the player to search all boxes, and the second one makes the system useless after a few hours.
Changing the amount of food required is a bad idea due to the difficulty level. Maybe some people enjoy searching every box for food crumbs, but not me.
If they increase the cost of a long rest due to the difficulty level, why play as a long rest based character when others can do the same or even better.
Then, instead of wasting food for a full rest, you only eat a small portion.
I'm not buying an argument to play at a lower difficulty level.
I like difficult fights, but if I wanted to play a game about managing food supplies, I would buy a survival game instead of BG.
So, to sum up, it is better that the cost of food is not related to the difficulty level (maybe you can remove the requirements completely on story mode)