Oil pressure when cold.

I've always seen the pressure be higher than normal in colder temps when the engine is dead cold, If the pump can move the oil.

that would be logical, and consistent with his statement that the truck normally runs at 40 when cold, 20 once warm

if it were my truck I would get a basic oil pressure gauge, pop the hood and see if I couldn't hook it up in the engine bay for checking purposes
just to verify if the reading on the stock gauge is correct or not