The other point about this that no one has touched on is that the procedure was introduced without any advice to ATC that the change was to be made. (At least on this side of the ditch)
A trifle arrogant perhaps??
We first heard about it from the kangaroos mouth one morning recently when the driver airframe of a flight that appeared to have stopped in relation to the others mentioned that QF had a new descent speed profile where they descended at cruise mach no till transition to IAS, and then 250 kts.
Not very friendly to following traffic that's able to fly anything from 280kts up to 350kts for a 74.
Oh well, I guess QF just has to expect to see the sun or moon going round the aeroplane occasionally if they aren't able to foot it with the rest, and how that saves fuel or costs beggars me.