While testing LPS-84785 I found that Indexers add search terms generally to the query. This means that if the JournalArticleIndexer adds a non-localized title, the query will look in all asset types for a non-localized title. This can be a problem because some indexers are not yet fully localized and may cause poor accuracy under certain conditions. Components affecting the general query:
If you explore the query sent to the search engine, you will notice duplicate query parts of fields such as Field.TITLE.