I think it's all about imbalances of water/electrolyte value, as that Stanford study points out, especially imbalances that happen quickly over the course of hours and days.
Given long hikes and activity calorie burns of 1500+ in one day (easy to do in a few hours up and down the mountain) with possible daily caloric deficits, it's important to note that your body isn't just sweating, but is also possibly entering a more ketogenic state and burning pent up glycogen. Because glycogen molecule is bound to 3 water molecules, in addition to normal exertion/heat sweat, water is being released from the system simply because of how the body is fueled - which puts things out of balance quickly. Many folks may know this phenomenon in weight loss as the first 5 pounds of "water weight". In the keto/low carb world, there is a cure for this called "snake juice", which is just electrolyte in water.
So in the case of a lot of calorie burn and caloric deficits on a hunting trip, adding electrolytes makes a lot of sense to keep the water/electrolyte ratio where the body is used to running. A good salt/potassium mixture is important, personally I use oral rehydration salt packets (or part of a packet). Most importantly, listen to your body - if you're dizzy and weak after a long hike, you might need electrolytes in addition to water.