I would assume that it’s neither a UI issue nor a problem with the source data, but rather a limitation of the routing engine.

Looking at your link, it does seem to say that support is experimental.

I get “Metro Navigation in this region is not available yet” (region is Northern England, UK) from Organic Maps.

OSMand says “Unfortunately OsmAnd could not find a route suitable for your settings.”

The Open Street Map website itself only gives foot, bicycle, car as possible options for directions.

I think the info just isn’t there yet.