Interesting, thanks!
I note that they were specifically for the longest haul flights...
In 2004, Singapore Airlines' Airbus A340-500s were no standard aircraft. Indeed, they were operated on the world's first- and second-longest routes: Singapore to Los Angeles and Singapore to New York. When Singapore Airlines started operating the Airbus A340-500 to New York, this route was deemed the world's longest - 9,500NM (15,300 km), translating into an 18- to 19-hour flight.
...were probably never used and haven't been in place for 10 years or so.
Back then, cabin crew trained to work on Singapore Airlines Airbus A340-500 were instructed to use the corpse cupboard in case no free row of seats was available in the cabin to lay out the deceased person and cover their body. However, according to an airline's spokesman, the cupboard was likely never used until these long-haul aircraft exited the fleet between the end of 2013 and the start of 2014.