The toyota pumps use mechanically controlled system that move the position of the rotors in relation to pressure in the pump - the purpose being to not generate more pressure than needed. Its not tuned to viscosity or oil type, its tuned to pressure.
To further complicate matters, they added an electronically controlled bypass valve that lowers oil pressure (to save fuel presumably) under certain light load conditions - ie under a certain RPM and under a certain calculated engine load. Said valve is controlled by the ECU.
However it is actually 5000 miles, because every 5000 mile interval in the service section says:
NOTE: If 0W-16 oil WAS NOT used at
the last oil change, replace engine oil
and oil filter.
I guess I will find out how all this works over time, as I own one, and I like to keep my cars forever. I'll keep you posted