I've realized that when a non-standard filter (https://moodle.org/plugins/filter_multilang2) is enabled and applied on "Content and headings" it isn't applied to the course fulllname [1] when displayed in the app (it's applied correctly in the course summary [2] and content).

When doing the same with an standard plugin (https://docs.moodle.org/31/en/Multi-language_content_filter) the course fullname is shown correctly (with the filter applied) [3].