Discovered when working on https://phabricator.wikimedia.org/T356794. On 7.4.6+ (and earlier builds with Watchlist filters):
- Set your device to English if it's not already, and add some Chinese variants (like Simplified or Traditional) to your Wikipedia languages
- Open your Watchlist, tap to open Filter view
- Observe the Wikipedias section
The localized language names should be displayed for all items in this section.
No Chinese variants are displaying their language names in this section.
I think this may be because the language variant codes don't seem to be transiting for these WKLanguages.