The average sedentary individual is way more likely to be dehydrated. Physical exertion is going to deplete both hydration and salts, via sweat.

I am a runner and a weight lifter and a former Sergeant in the army. Dehydration is overwhelmingly more frequent than electrolyte depletion. Even when there's no physical exertion involved.

If you're eating food then you're fine. The US military tells everyone to drink water until your piss is clear. "Hydration charts"

The U.S. military does not have any uniform guidance on this. The Navy and Marine Corps official guidance is that urine should be lightly straw-colored. Hyponatremia is warned against just as strongly as dehydration.

The military has like an hour of exercise a day, no? If you are walking 10 feet to a car and driving to site in a cube all day, I don’t think you have the same hydration needs as someone physically exerting themselves.

I think the point was that if you exercise a lot, eat enough, and drink yourself to clear pee, you still get enough electrolytes. So a less strenuous plan with enough food presumably also means one gets enough electrolytes.

You'll still be low on Magnesium if you sweat and perform for 60min+ — which leads to stuff like restless legs and rather bad sleep.