Yeah I know, but it is wrong to add not existing features to osm. Only because Openrailwaymap renders them, doesn't mean it's right.
However they recently added support for the openhistoricalmap data. So this should be rendered in it as well. It is documented in https://wiki.openstreetmap.org/wiki/OpenRailwayMap/Tagging https://wiki.openstreetmap.org/wiki/Tag:railway%3Drazed that you should use openhistoricalmap for the non existing features.
Here is the news, where they added support for it, this year: https://forum.openhistoricalmap.org/t/openrailwaymap-adds-openhistoricalmap/446