I thought this, but then remembered a discussion about an RCH not being a fall arrest system either, unless paired with dynamic rope. Correct me if I'm remembering that wrong.
With static rope, we would seem to need a full body harness with some shock absorption sewn in, for safety, and then a saddle, fleece or otherwise, for positioning/hunting.
I'm not saying that it's safe, or according to a standard. But it was at least attempting to point at something that existed already.
My point is that in the last 3 or 4 years, I have watched hundreds of people come through this site, taking a pile of things for granted on their way to using saddles and ropes and hardware for climbing. I can only imagine that there's thousands more that I'm not exposed to.
It is reaching a point where I can't see an outcome that doesn't involve some broken backs and legs.
A rock climbing harness is designed to absorb and distribute force to a human body in a certain way. It is tested to certify that it will not break prior to distributing that force in the event of a fall. It is up to the user to use equipment and procedures that eliminate the risk of forces beyond that threshold. If they succeed, they can be reasonably certain that their RC harness will perform as expected. Because of a huge body of institutionalized knowledge experience and testing.
If a person climbing and hanging in trees wants to use a rock climbing harness, he can. All he can reasonably expect, however, is that it will absorb and distribute force to his body up to the amount specified by the testing procedures, guidelines in the industry, and clearly stated by the manufacturer. If he decides to use equipment and techniques that don't eliminate the risk of exceeding that force threshold, he is now playing russian roulette.
The only way for a "saddle hunter" to determine if he is engaging in behavior that introduces the possibility of exceeding that force on his RC harness is to think critically, and do math.
And the only way to know what type of damage/injury that forces up to that force threshold will inflict upon him, is to seek guidance from regulations in other institutions.
All of which is the point I'm trying to make. There is no "there" there for hunters. TMA requirements on fall protection seem to mirror OSHA requirements for working from heights if I remember correctly. And the single biggest reason for this is lack of consumer engagement. We will get what we want eventually by sacrificing some fellow hunters, or by putting in effort ourselves to develop an institution. Choice is up to us.