I <s>I have no idea why Wikipedia shows one map but not the other.
other.</s>
*edit:* Since you only entered the wikidata ID to the Yokine relation 10 days ago it might be that the underlying Wikipedia database just hasn't picked up the change yet.
As to the search results: It appears Nominatim has joined both relation and node for Noranda ([link][1]), thus only showing one search result for both, but kept them seperate for Yokine ([link 1][2], [link 2][3]). Maybe Nominatim hasn't recognized the quite recent addition of Wikidata tag in its joining yet? I can only guess here.
I would surmise that the odd Nominatim behavior has nothing to do with the Wikipedia map problem. But who knows.
[1]: https://nominatim.openstreetmap.org/ui/details.html?osmtype=R&osmid=11689262&class=boundary
[2]: https://nominatim.openstreetmap.org/ui/details.html?osmtype=N&osmid=1546128372&class=place
[3]: https://nominatim.openstreetmap.org/ui/details.html?osmtype=R&osmid=11689254&class=boundary