This is how I understand it. Also you get the added benefit of additional thermal capacity due to the extra oil keeping things in the ideal operating range when everything is working harder and generating more heat.FWIW: Perhaps the "off road" is designed to reduce the risk of oil starvation in "extreme lean" (>25deg) events rather than off road/ overlanding trips where lesser gradients might be experienced.
People forget that oil takes out almost as much heat from an engine as the coolant. Followed up by air flow in the engine bay. Then a distant last is the exhaust flow and scavenging effect.