My 1MM was somewhere over the Pacific SEA-KIX in 2010 on DL Metal... I had read about these announcements and thought the FA and Crew knew and I was waiting for the announcement ... Nothing
My 2MM was somewhere over the Atlantic CDG-RDU in 2016 also on DL Metal ... this time I had spoken to the Diamond Line agent and brought it up during ticketing .... and still nothing
When my wife went into labor a week early and I needed to get back SFO-ATL-RDU as fast as possible, the crews on both flights knew about it, made an announcement and I got a bottle of champagne on both flights. DL did it right on those flights ... btw, I was 3 hours late, but all was good, great actually.
We will see about 3MM, though it is much more difficult now (at 2.7MM).