The only reason I would want the damper is to be able to snuff out a grease fire. But the better solution for that is to not get the grease fire to begin with. If kept clean, cook managed correctly, it should not be a concern.
I'm a stick burner guy. I want air flow through my cooker. Ya get better convection. I realize there's some " trendy " young people in Texas who are closing off the stack on their stick burners to create more smoke at the start of the cook. If it works for them, then great. But I bought my first Kettle in 1989, my first WSM in 2002 and I've never shut down the exhaust on any cooker I"ve owned. Not gonna start now.