The current "Results from sister projects" is misleading (people may think the results are in main namespace). Compare the local result in the left side
|mediawiki/extensions/CirrusSearch||master||+124 -31||Correctly prefix snippets on external titles with the namespace|
This looks to be caused by the text highlighting. If we search for User: "greetings from new zealand" the interwiki result is displayed as User:Robin Patterson, but if there is highlighting available for the title that is used and it does not include the namespace prefix. In full text search title highlighting appropriately provides the namespace prefix.
This is certainly a bug in CirrusSearch.