Rigbyrigz: The FMC does not downlink every legs change. I think it is HIGHLY unlikely, as I've posted above, that the aircraft was logged onto Kuala Lumpur ADS (WMFC) at the time the FMC was reprogrammed by whoever was altering the flight route. This is extremely easy to verify.
If it was logged on then it could have conceivably have downlinked the change in next waypoint ONLY, but after flying 777's for 10K hours so far I'm still unsure whether it does this immediately the change is executed in the FMC or at the next waypoint/18 minute reporting interval.
Either way, as stated previously, unless the crew had manually initiated an ADS log-on ATC would be clueless what they had in their FMC.