Perhaps you should speak for your own carrier then. I have not met one person here who has not stated that our 737 op is anything but the most physically exhausting flying, ever. As a matter of fact, I've never heard one person claim that night freight of any kind was other than exhausting and debilitating. All the research suggests that failure to follow the circadian rhythm is dangerous, leads to premature aging, lowers metabolism, suppresses the immune system, heck there is even an article circulating on Facebook claiming that it outright causes cancer.

As a new hire, I was told point blank "You will fly tired." I didn't get it. There was nothing in my previous experience that prepared me to even comprehend the level of fatigue that is my new normal. I am fatigued every flight. Every single time I got in the 747 or 777 I was going to be exhausted at some point. Everybody now on the 737 says its even worse than the heavies.
Sure, there isn't a whole lot of flying involved. But neither is there a whole lot of rest. And what rest you do get is precisely opposite of the natural cycle.