Yes I’m sure you are right. I hadn’t noticed his age—in the photo I took him for a younger man.
I was thinking that with the adrenaline burst a guy could almost high-jump out of the trackbed. But I would agree with you that the surprise of being down there (especially since he was pushed) and the shock of the train bearing down might have frozen him in place.
Since you asked.....there is a crawl space under the ledge his hands are grappling onto. He panicked. But if he had not he could have crouched in the crawl space and missed the train by inches