ITT as reference in formation flying?

[JayPee]

Recently I watched a stream of ZeroMass and Snooze's BAI flight. If I've understood them correctly they were using their ITT as reference to match speeds for formation flying given that their weight/loadout was roughly equal.

Did I understand this correctly? And if so, how accurate is this to e.g. referencing fan RPM? I'm not an expert on aircraft engines but I'd personally consider the temperature in one part of an engine to be a more of an indirect derivate instead of a direct predicator of speed like the fuel flow or the RPM.

I couldn't find anything about this in the 74th vTS Formation Guide Change 3. However, I do vaguely recall a tutorial on AAR where the author mentioned something about ITT to match the tanker's speed but I'm not quite sure anymore. I couldn't find anything about this either in the 74th vTS A-10 Air-to-Air Refueling Guide Change 1.

Thanks