The language selector organises languages by region. There are some languages that belong to multiple regions and some of those are identified as Worldwide. Worldwide languages such as Spanish should also appear under their corresponding regions, but that does not seem to be the case currently.
This seems to be a regression since I recall this working as described before.
For example, when viewing a page available in many languages using compact language links, you can see that Spanish ("español") does not appear in Europe or America regions where it should appear in both of them.