When I remember correctly iD told me that I should add "network:wikidata" as well as "train=yes".
I read here:
https://wiki.openstreetmap.org/wiki/Key:train
"This tag is mainly used for trains which are not a tram=*, subway=* or monorail=* train. It may overlap with light_rail=* in some cases."

I don't have strong feelings about this. Feel free to change it or I change it.