Before the text was changed from “No results were found.” to the “your community is brand new” version, the text matched both cases. Since “No results were found.” was re-added for searching, I thought it could also be shown in this case without me replacing the string for all languages.
Or maybe visiting /u when the directory is disabled should work the same way it works for anonymous users when hide_user_profiles_from_public is enabled - they cannot open the directory at all.