Fast240Z

I was just outside, working on my Z, getting it ready for my head swap. I noticed that on my '72 carburetors, there is a hose that goes from the thermostat housing, to a pipe that goes through the intake manifold, and then out to the coolant hoses that run along the back of the vehicle. I have a set of 71 carbs (round top, just like my 72's) with intake manifold, and this manifold is missing the coolant passage. Is this for emissions, to get the carburetors to reach normal operating temp faster? On the head that theramz gave me from his 260Z parts car, the thermostat does not have an outlet for this coolant passage, which gives me the idea that this is for emissions. Am I right in my hypothesis?