Well, I think they do to an extent. I do not believe though that any scent killer product can truly get rid of all human scent. A little cover scent, and using the wind to your advantage, and I think you are fine. Heck, I have even used diluted apple cider on occasion when hunting in an apple orchard, or if I forgot that, I would take an apple andcut it open, then rub it on my hat, shoulders, pants, etc. Seemed to work for me. Heck, no deer that is downwind of you in 20 mph winds is gonna stick around too long, scent killer or not.
I always shower with scent killer body wash, use scent killer and a cover scent and then hunt downwind of the deer. Does the scent killer work? Dunno for sure, but the entire program seems to do the job.
As I sit and glass, which is common for hunters out west, I have sort of quickly discovered something I never learned when I was younger.
In my youth I had enthusiasm and spirit. In my middle to advancing years I have creaky knees, arthritis, and I tire more easily than I used to. Where I used to sit on the cold hard ground I now look for that soft spot to sooth my tired muscles. That leads me to my tip.
Carry your soft spot with you!
In my pack I carry an air filled, ultralight, camping pad....