And,... when your B767 heads off to Perth climbing to FL380 and requests amended FL260, the TAS field stays the same unless we manually change it.
And that, like I said, is the start of the problem. What a ridiculous system... Obviously programmed by someone with no idea of high altitude aircraft performance.
Your system should have the ability to generate a TAS based on the level the aircraft is AT, not based on the level the aircraft is planned! So simple, and so stupid they didn't program it that way.
So I hope we have debunked the blame from pilots who most of the time do cruise at their planned Mach no, it is the ATC system that incorrectly reports planned TAS when pilots cruise at other than their planned level, which of course they do regularly due winds turbulence etc.