NobodySpecial, you have that part totally right.
Most of us should be able to go ten days at least before depleting vitamin or mineral reserves and possibly much longer on stored fats for calories.

One of the main reasons to teach trapping and foraging along with shelter building is to keep people from wandering off.
If they stay near the wreck or last known position they are easier to find.
Setting up a shelter, a fire and doing a bit of food gathering also helps people mentally. It helps them if they feel they are doing something positive to help themselves survive.

I wonder how long it has been since we had a thread about what the priorities for somebody who got lost or marooned are?