I used to jump off that way all the time.
I loved the feeling of stepping off a moving train, leaning backwards slightly, so the momentum would just straighten me right up!!! Then a couple of quick steps and you were on your way.
On rare occasions I'd get to grab the grabiron just as the train began to move, however this was harder to do as the traincrew usually gave the "all clear" once they saw that everyone was on board and if you were hanging back, they would see that you either got on or got away from the train.
I managed to do it much more frequently when I worked for the road.
I remember working a parlor car and got off at Southampton to help some riders carry their luggage to their taxis. (Remember: tips!!!!)
By the time I got back to the train, the conductor was waving furiously at me to get my butt on the train and the train was moving. I was no where near the low level, surfaced platform (it was one of those LONG parlor trains where all the cars did not make the platform), and I couldn't get there in time, so I stood where I was, on the ground, and, as the steps approached me, I grabbed the grabiorn in true railroading style and stepped onto the bottom step . . . . only to find that as I was much lower than I would normally have been had I been standing on the platform, my foot missed the bottom step and all my weight was suspended from my arms on the grabirons. I pulled myself up and got onto the steps. By then the train was making a pretty good clip. I shut the trap and shut the lower half of the dutch-door and hoped nobody saw me!
Had they still had mail cranes at that time, I'd have probably been yanked off the train as I passed by! Sort of "returned mail (male?)!"
Dave Keller