What was Mace Windu's connection to the Whills supposed to be in early drafts of the script for Star Wars?

George Lucas’ first draft of the synopsis of the script for Star Wars – written in 1973 and titled "Journal of the Whills" – is said to begin as follows:

This is the story of Mace Windu, a revered Jedi Bendu of Ophuchi who was related to Usby C.J. Thape, Padawaan learner of the famed Jedi.

Lucas explains the original "Journal of the Whills" concept in Star Wars: The Annotated Screenplays:

Originally, I was trying to have the story be told by somebody else; there was somebody watching this whole story and recording it, somebody probably wiser than the mortal players in the actual events. I eventually dropped this idea, and the concepts behind the Whills turned into the Force. But the Whills became part of this massive amount of notes, quotes, background information that I used for the scripts; the stories were actually taken from the ‘Journal of the Whills’.

Elsewhere, he has described the Whills as "immortal beings" connected to the Force.

As we know, he eventually dropped the "Journal of the Whills" idea, and made Mace Windu a Jedi who died in the Clone Wars.

I’m curious as to why Mace Windu would have written a journal named for a race of immortals. Was he originally conceived as one of the immortal Whills? Or did Lucas come up with the idea that the Whills are immortal later in the writing process? What was Windu’s relationship to the Whills initially intended to be?