I marvel that you don't see any contradictions. I've pointed them out to you before, so I'm not going do it yet again. But you are demonstrably wrong on this score. Though since the CT/MT material about nobles is so scanty as it is, the effect of the contradictions is considerably less.We (you and I) disagree on it, in no small part, because I don't see any contradiction in the T5 fluff nor Fief mechanics with the CT/MT sources,
...but do see that the T5 playtest materials from 8 years ago or so were ignored and counter-written in the GTU.
GT:Nobles was published in 2005. If Marc told Loren and Jon that this was the way he wanted things from now on, I'm quite sure they would not have ignored him. He did, in fact, tell them to include viscounts and they complied. So that argument cuts no ice with me. Marc approved Nobles for publication. If he had a finished draft lying around at that time, he should have revised it.
T5 isn't a force retcon to the GTU - but it is clearly not the GTU, and is explicitly the OTU.
I don't know what you mean by 'force retcon', but you're right that T5 is clearly not the GTU. Nor is it the old CT/MT Traveller universe. And since the GTU is supposed to be identical to the OTU up until the change point, any retcon of the OTU is strictly speaking a retcon of the GTU too. However, with the low likelihood of any more GT modules, that is probably a moot point.
Hans