Honestly, it sounds like it's a random crap skill to me. Not that the skill itself is crap but that all the ideas they have is just stuffed in there because they have no other skill to put them in.
You can be a master chef while being able to create poisons and healing powder, knows how to skin creatures and not only that, you also know how bullets work. (I'm sort of a chef and I have no idea how to create poisons or how bullets work, bug I guess it's all explained my Fallout Logic. :shrug: )
So it seems like they had some great ideas but nowhere to put them in a skill so they just came up with survival and dumped everything in there.
Hm, Josh, I see you watching there. Mind correcting me?
First I'd like to note that when you, specifically, say "Fallout logic" it can be inferred to mean from context "no one has explained this" not "this cannot be explained".
Survival does not affect the crafting of ammunition at reloading benches. Repair affects the crafting of ammunition at reloading benches. Survival affects the crafting of things made from animal parts and plants: typically prepared food items, hides, poisons, and primitive chems (like Healing Powder). It is not a random grab-bag of goofy stuff.
Yes, knowing what plants to combine to make a poison is covered by the same skill that determines if you know how to properly tan a gecko hide. This is in the same system where the same skill that allows you to repair a handgun allows you to repair a Tesla cannon and the same skill that allows you to use stimpaks effectively also covers basically every piece of human medical knowledge. SPECIAL skills are broad and abstracted.