The misconception being used here is the thermostat opens to provide the heat. It doesn't. It opens to allow the water to flow throught the radiator to cool the engine down. Even when the engine is ice cold it's circulating coolant through the heater core(as regulated by the heater control valve). The thermostat does NOT close off the flow through the heater hoses. By installing a lower temp rated therostat you actually are reducing the heat process by allowing the heated coolant to flow through the radiator sooner. A higher temp thermostat(like a 190*) would keep the coolant from flowing into the radiator until it reached the higher temp so that the coolant flowing into the heater core would be allowed to reach a higher temperature. However it doesn't make the coolant heat up any faster(from cold until say 180*). It just causes it to be heated longer before it's allowed to be cooled by the radiator after the t-stat opens up.
