The knowledge that those were actual roaches will likely give any viewer a new appreciation for the scene after rewatching it, especially when realizing that some of the actors in the train car were on edge with their reactions to the roaches and the random directions they could have scattered in.
I think we can all relate to Alison Wright on that last statement, except for maybe those animal trainers, but still cockroaches wouldn’t have had quite the same skin-crawling effect as the active ones inspired during that scene.