I don't think so. The OP was told by the DL Diamond phone agent that he was rebooked in Business Class on Singapore Airlines. He discovered by accident when checking his reservation online from the inflight wifi that the Diamond agent had erroneously booked him in SQ's First Class Suite.

Also, taking the original DL flight, he arrived in SIN around 1AM. The SQ flight arrives around 3:30 AM. I'd say that the 1AM is far more desirable as far as getting a full night of sleep goes, and not sleeping away his whole first day in SIN.