Sintered pads installed by the dealer
After going thru the heartache of forking out for new pads and rear disc because the 2nd set didn't last 6K miles either, before ordering a spare pair at home I checked with the dealer to confirm whether using sintered pads would be an issue and they confirmed they are now standard, or at least for my 2013 which they fitted new pads on along with the new disc.
So my hope is they last considerably longer, at least beyond the next service. I'll get some EBC sintered spares, but I'm really hoping not to have to add another comment on this thread for at least another 10K miles ...