I'm sure an editor travelling at the front or back of a train departing from WA station would be able to watch the curvature of the track and confirm whether it's the gentle curve to the left that is depicted on OSM or is travelling by a different route, especially if it seems to involve leaving from the other end of the platform and/or a "near 90 degree turn" somewhere. That wouldn't be sufficient evidence to copy a route from another source (unless it's official DLR/TFL opendata) but would indicate whether more detailed study is needed.