Localized posts with different languages have a number added to their permalink if the title is the same.

[ironland]

When localized versions of posts with the same title are created with Polylang manually in WP, the localized permalink structure handles it so that there's no -2 etc added to the end of the permalink.

With the importer, the post is saved before the translation connection and in that moment it is in the same language as the primary version of the post. The translation is created only afterwards and at that moment, there's already a -2 in the permalink of the translated post.

This would be an issue for example when importing events or movies that have the same name -> title in each language used on the web site.