For clarity, my take on this topic is not about position exactly.
It is about weight distribution between the hands and saddle, as the contact points. When you ride outside, you get a pressure pushing the upper body back. I contend that the push in this case leads to a slight shifting of force, off the hands and on to the saddle.
Inside, we lack that force, and I predict that we end up with a bit more force on our hands than when we get the push from the air flow.
I have tried to come up with a way to accurately test and measure this. Essentially, a wind tunnel and force or pressure measurement under the saddle and hands would be ideal. Test with no wind load. Then apply wind load and see if there is a shift.
I don’t have sensitive enough equipment to test in the wild, so I just have my theory for now. Maybe I need to send this to Specialized as an idea for the WinTunnel testing?