I typed "mac safari code block source" in the Title field and the below + some more suggestions shown. The first two are pointing to the third one. And also having the Possible Duplicate: link reference inside it. So is the first two suggestions really helpful in any of the case, as they are increasing the suggestion count?.
That does look pretty odd when all of the duplicates are using the same keywords - but that's not always the case. The reason we leave duplicates laying around is they are great sign posts. Duplicates usually get asked because the person couldn't find the duplicated question based on the words they searched for. So it's perfectly possible that the particular words you type into your title would only bring up a duplicate question which would then direct you to the main question where you could find an answer.
Duplicates also aren't always exact, as in the underlying problem may already be available in another question or a FAQ - someplace you might not have expected to look. Maybe that other question is listed in the duplicate search, but you don't look at it because it doesn't look like the perfect fit. Instead, you visit the duplicate question which indicates "yes, you can find your answer over here." If we only showed you the final destination's title, you might think your question isn't answered anywhere and wind up asking another duplicate question.
So while in some cases it does look like we're just wasting space, showing duplicates is extremely valuable in other cases.