I think it has more to do with lighting as well as the height of the ceiling. In NYC the escalator going to Grand Central Madison is very long and yet it doesn't feel uncomfortable at all. It has way more lighting than your picture and the ceiling seems higher too.
Do you feel nothing at all when you're on a very long escalator and you look down? What if someone pushes you, or a person behind you? People would fall like domino.
I'm going to guess the person suffers from vertigo, as have I to a small degree - particularly on the metro escalator in Rosslyn, VA (across the river from DC). The sensation occurs going down or up very tall escalators in a tunnel. When it hits, you feel like you are traveling horizontally with some weird tunnel vision. This is terrifying and can cause you to feel like you're falling - even when you know you are going down or up, your eyes are telling you you're traveling horizontally.
I've also gotten this driving a car through long tunnels as well, going down or up (Baltimore 895 harbor tunnel can do this).
I’m pretty scared of heights and generally haven’t been triggered by any long escalators into subways, but there’s one on the DC Metro (Adams Morgan maybe?) that kind of freaked me out.
