In [[//it.wikipedia.org/wiki/Discussioni_aiuto:Interwiki#Sidelink_a_categorie_su_Commons.3F|this discussion]] we've just decided that among the sidelinks of a it.wiki article, in absence of a respective gallery on Commons, there should be a link to the main category related to the article (see property p373 on Wikidata).
I don't know if it's already such this, but I noticed that in [[//it.wikipedia.org/wiki/Vittorio_Emanuele_II_di_Savoia|it:Vittorio Emanuele II di Savoia]] the sidelink to [[//commons.wikimedia.org/wiki/Category:Victor_Emmanuel_II_of_Italy|commons:Category:Victor Emmanuel II of Italy]] doesn't appear.
Conversely, in [[//it.wikipedia.org/wiki/Domenico_Tarsitani|it:Domenico Tarsitani]] it does appear.
In both of them the template:Interprogetto (similar to Commonscat but suitable for all the link to the WM projects) doesn't have parameters and takes the data from Wikidata. And in the respective Wikidata items the link to Commons is defined by the property p373 and not in the "Other sites".
I don't think the problem is in the template:Interprogetto, since its synthax is pretty simple and I don't see why it should behave differently.
Can the problem be fixed?