Larry, for background, I have never used a tree stand, but have a small amount of mountaineering and rock climbing experience. If/when I use a treestand, I will likely not have cell reception or a rapid emergency response time even if I have cell service.
Also, I have been to a class, where a doctor from the midwest talked about the people he had seen or heard die in his state due to suspension trauma (without any other injuries) from hanging right side up in a full body treestand safety harness and waiting for help. On the other hand, I have seen people fall while rock climbing and they fall facing the wall where they can use their arms and legs to avoid trauma against the wall, and they fall or pop up right immediately...and don't suffer suspension trauma if they are conscious because they can push away from the wall and sit back in their harness, rather than hanging from the top of their back with all of the force on their thigh straps.
So, I understand how the full body harness systems with the controlled descent emergency attachment/release would be the safest way to go for using any treestand.
But I don't understand how I would be safer in a full body/vest type harness than a climbing harness, if I don't have a controlled descent system attached to my harness? With some safety rope foot loops and lines around the tree available separate from the tree stand, and my whole stand fell off the tree, it would seem that I would better be able to utilize these to lower myself down safely in my climbing harness? If I am wrong, why am I wrong to think this? I might want to get a stand system someday, and already have an Alpine bod climbing harness, but I would not use this, if it would not allow me to self rescue.