Hi, dauphinois here.
First of all, let met tell you I absolutely love these map dev diaries! The granularity is insane for a game of this scale.
Secondly, let me preface by saying I have not studied history or anything like that but I have a few interrogations. It is possible I am completely wrong about these next sentences as I am but a mere Maths Teacher.
I do not know what "Dauphiné valentinois" refers to even after searching a bit for the term online. It seems like a mix of two different things : The "dauphiné" (which could be called "Le Dauphiné De Viennois" but in 1337, the capital of the Dauphiné has not been Vienne for 200+ years if I recall correctly) which is a state of the HRE in 1337 (which is named "Viennois" sadly on the political map...) and the "valentinois" which joined the french realm in 1316.
It is the Dauphiné that will indeed be sold by the last "independent" "dauphin" Humber II in 1349 to future king of France Charles V.
As I said, in 1337, the capital of the Dauphiné is now Grenoble and has been for a while so is it possible to consider a name change from "Viennois" ? To "Dauphiné" or "Dauphiné de Viennois"?
On a side-note, I think "Viennois" was never used to call the whole Dauphiné but only for one the four countries of the "Bas-Dauphiné", the one surrounding Vienne (obviously) afaik.
"Dauphiné" is really the important word imo as its was called "Le dauphin". When it got acquired by the french realm, the tradition stayed and the oldest son of the king became called the "dauphin".
Thank you very much for these reads and delicious screenshots!