(....)
Not exactly. There was no steadfast rule saying that the HRE had the authority to upgrade anyone below his rank. In fact that idea is mostly a load of tosh. In the case of Burgundy famously trying to be made into a Kingdom it was a gambit to declare independence from France with the backing of a powerful state - to do it alone would bring the wrath of other Kings, seeing the Burgundians as upstarts; the HRE supporting it would mean that most places would accept it. Secondly, the only times that HREmperors really upgraded nobles to higher ranks was when those nobles were direct vassals of the Emperor. It was any noble's remit, whether Emperor, King or Baron, to make another man his vassal and grant him a title beneath his own, so long as it were as a noble of his own realm. There was nothing saying the HRE had the power to do so outside of his own realm.
Let's not forget that the dukes of Burgundy also held territories in the Holy Roman Empire, like the duchy of Lothier, Brabant and Limburg, duchy of Luxemburg, free county of Burgundy (Franche Comté), county of Holland, Zeeland and Hainaut etc., so any promotion could and probably would only include a territory in the Empire, but the duchy of Burgundy (and probably Flanders and Artois too) would (at least at first) remain a nominal part of France. In most propositions of such a kingdom all other imperial territories held by the Burgundian dukes would have been made a part of this kingdom. Instead of Burgundy, Lotharingia, Frisia and even Brabant (like Lorraine a successor of Lotharingia) were proposed; and another concession was the right of female inheritance or at least through the female line.
This last provision would IMHO been a more likely way for the Habsburg emperor to get a extra royal title in the empire, then if he would have created one for himself.
When Charles the Bold was negotiating with Frederic III about his Royal promotion, they were also discussing the possible marriage between the heiress of Charles (Mary) and the heir of Frederic (Maximilian) and it was unlikely for Charles to get a heir, unless he would survive and has the chance to remarry in old age.