The new preference option, MediaWiki:Monobook-responsive-label, has already been translated to many languages on translatewiki.net.
However, it seems like l10n bot does not import these translations to the software.
Steps to reproduce:
- Go to [[Special:Preferences]] on any Wikimedia wiki.
- Change your skin to MonoBook (if you don't have it already set).
- Save your preferences.
- Change your interface language to Hebrew (he) or German (de) or any other language to which the new preference option is already translated.
- Go to the second tab in your preferences.
- You should see "Enable responsive MonoBook design" instead of the translated label.