The thing is you're adding about 3500 miles of travel with that itinerary, plus a multi-hour layover. I don't know about you, but NOBODY's Y product is worth is worth adding a short overnight redeye and turning a 10ish hour nonstop into a ~24 hour backtrack. Y is still Y, even if SQ is better than DE.

Now, I realize this is FT, where there are people who would probably fly JFK to LAX through SYD, EZE, JNB and DME if it would get them status or Krug and showers, and there are probably even some people that would find that routing appealing as a Y passenger because they love airplanes, but... CX J MLE-HKG-SEA-CUN (last leg AS F)? 50k. 5k less than flying SQ Y/DE J. And the CX J hard product might be a BIT better than SQ Y.