Set Up:

In the video, you can see two boxes, each with a rail going through the middle. In the left (red) box, the floor is elevated by a half slab on the villager side, on the right, the floor is on rail level.

In both boxes, a villager is let free to go to a work station, which lies on the other side of the train tracks.

Current Behaviour:

Rails are considered as a walkable block, if an NPC (only tested with villagers) stands on a half slab next to the rail, but not as a walkable block if the NPC stands on the same level as the block.

Expected Behaviour:

Rails to be considered as non-walkable block in the case an NPC wants to walk from an adjacent half slab over the rail, as it is when standing normally next to the rail.