I had this issue also pop up, and I'd like to report a couple findings of digging around.
This issue appears related to
118380, as the position of the player bounding box appears to no longer be able to move as far into the out of map tile. This behavior also appears loosely related to the landfill bug behavior
FFF-346, as we now cannot get the collision box of a player off of a tile they can stand on.
I was testing player movement (no exoskeletons, etc), and how close the player collision box can get to the box of the train appears less than consistent in both 1.1 and 2.0; a player is stopped at different points when walking into the side of a train or wagon (1.1 & 2.0). However, as long as a two boxes don't intersect, then the player doesn't take damage when the train is moving. In relation to this bug report, the player seems to be pushed off the map when they exit, and while the collision boxes don't contact each other, the player can't be snapped "in bounds" onto the map tiles with the train still there.
Also related, players at the edge of the map can be hit by a train due to the player's bounding box no longer being allowed off of the map tiles, and the player and train's boxes barely contacting as a train passes.
As mush as I don't like the change, it seems fully intentional overall. A potential fix might be to slightly shrink the width of the train collision box.