There is no reason why the ProtectionForm expiration dropdowns should be in the content language since it doesn't change the submitted value. The issue is that items in the dropdown are defined in the message.
This applies to:
- Core (ProtectionForm.php)
- FlaggedRevs (FlaggedRevsUIHooks.php)
- ArticleFeedbackv5 (ArticleFeedbackv5Hooks.php)