Okay, after two days at the dealer, they did loan me a 5.0 Mustang to drive, this is what they found. First, I have a 2019 ST, early build - September 18. They removed the drivers seat and took apart the back of the seat. They found everything was in place, channeling, access to the seat back for the air flow, in my case, mostly for ventilation. The design in my seats are to place the cooling/heated outlet to the top of the seat, around the shoulder blade area.
Having the top part of my back cooled/heated seems to be a bad place for that. The lower back is where I would expect the best location. My ST does have the lumbar support, not sure if that has something to do with it. The tech used his temp device to show the seat bottoms showed around 67 and the upper part of the seat also showed about the same.
I did voice that this did not seem to be a very good design, the tech just smiled, I understood his response, as the general manager was standing there. Now, this is my words on explaining what they did. With the internet these days, I am sure there are more knowledgeable members that will disagree with my wording, no problem, go ahead and point out what you disagree with.