Currently, when you reach special page for the first time with a search result, the namespace selection does not reflect the currently displayed namespaces. However, the namespace display should be correct.
- Enable the AdvancedSearch beta feature
- On any page
- Search using the box top right (top left if rtl)
- you'll see results for multiple namespaces (either user defaults or wiki defaults)
- hit the search button again (without changing anything)
- you'll see results for NS_MAIN only