Honestly, the “expert” is just another guy like me making a conjecture by looking at the same photo.
It is realistically a very good guess. Just look at other photos of the aircraft from before the accident. There are many of him sitting on the tarmac waiting. His head and helmet sit right in the middle of the bubble and right up at the top of the canopy. You can’t miss it. And given that at these speeds and G-forces you have to wear at least a 5 point harness and be strapped down TIGHT there’s no many other conclusions you can come to.
Even if he was passed out and his head rolled to one side it doesn’t look like there is any way his head could normally end up out of view. He’d just have it resting on the plexiglass or hung forward.
No need for that. As you see, I didn’t remember who - but the comment I remembered. Since I know nothing about planes, at first my thought was something happened to the pilot and then I read that comment.