The bit that I took exception to was the suggestion that current A359s are burning "2+ tonnes more per hour" than the B773. If that were true, the airlines that operate them would be kicking and screaming. We've got 17 of them in service to date and although there have been a few issues, fuel burn isn't one of them.
After analysing all the data from the last few years of operation, Airbus now reckons the aircraft is more efficient at higher cruise speeds than M0.85. We're being told that the typical cruise speed is being bumped up to M0.86-ish as a result.