Until we can talk to deer, many questions may never be answered...
IMO, carbon clothing MAY decrease your scent, but if you are upwind of a deer's nose, no amount of carbon or scent eliminating spray will save you.
With that being said, if you have done EVERYTHING just right, you may not bust a deer out of the area if they catch your scent, but instead simply make them edgy and hesitant about coming your way.
Maybe these products resemble "old scent" to a deer's nose. Maybe the lesser amount of scent makes a deer think that you are not still there but came through earlier in the day or yesterday...
I'm sure most of you have been mere feet from a deer's nose, but thanks to a "good" wind, you never got busted. I have worn carbon clothing and did everything right and got busted 100 yards from that same nose, sometimes even further.
I stopped wearing carbon clothing. My reasoning was simple. No one can tell me that if a deer comes in downwind from me, he will not smell me. I can be wearing ten day old clothes and smoking a cigar and if the wind is right, I will not be winded.
I'd rather be comfortable and play the wind the best that I can than be hot or uncomfortable and still get busted when the wind is not right.