Search not working as described in codex

[totatari]

In the codex it says if I sort my search query results by relevance it should behave as follows:

"Order by search terms in the following order: First, whether the entire sentence is matched. Second, if all the search terms are within the titles. Third, if any of the search terms appear in the titles. And, fourth, if the full sentence appears in the contents."

That actually is not right, because the third case never happens! Example:

I have 3 Posts with titles: "Keyword", "Key" and "Word"

If I search for "?s=key+word" the result ist only "Keyword" but it should be "Key" and "Word" too!?