Back in the days of writing the original SW, there was a point where Lucas depicted the rise of the Empire as a more gradual decline and fall of the Republic, rather than a power grab by a single dictatorial Emperor figure.
This was the idea in the January 1975 second draft, and it evidently persisted for a while - hence in 1976 Lucas had to tell Alan Dean Foster to take out references to it in the novelization. One slipped through, though: a mention of “the later corrupt Emperors”.
In the same conversation Lucas apparently mentions wanting Leia to become Empress at the end of the trilogy, and says he would have to discard or modify this idea if he kept to the storyline of a single evil Emperor figure instead of a more gradual transition.
So Kurtz’s idea here of Leia becoming a “Queen” does seem to derive from early SW concepts. (Including also the 1974 rough draft, where Leia becomes queen of her planet at the end, in a finale sequence much like the Triumph of the Will-style ending to SW 1977.)
A marker of how much the story had shifted to revolve primarily around Luke by the time of ROTJ is that in the story conferences there Larry Kasdan suggested having Luke, not Leia, become the new Emperor. (Lucas’ apparent idea during ESB of having both Han & Leia die in the third film, to clear the way for a Sequel Trilogy featuring Luke’s sister, likely boosted this marginalization.)
This is a great post that summarized the whole thing perfectly. Kurtz was seemingly referring to Lucas’ pre-SW drafts that were completely irrelevant by the time of ESB, and he tried to present them as the story draft for ROTJ (which did not yet exist at the time).