SLF here, but it's clear that (a) they were dumping and (b) they told ATC they didn't need to dump and weren't going to do it. So there's a conflict here that I can't quite figure out -- why would they commence dumping without telling ATC about it?
Is there some kind of auto-dump that happens on the 777 when the crew tells it they're planning on an overweight landing? Is there some imaginable software misfeature that turns on dumping automatically?
I assume the FDR will have been pulled, and that will presumably tell the FAA something, but I can't quite get my brain around how this happened.