I guess Tolkein found, like many artists, that, as a series of major works progresses, tweaks are needed to keep the sense of it going throughout. An artist may make thousands of such changes throughout the creation of each work, before it is presented to the public. It must be even more difficult when parts of the series are already vastly popular.
It is notable that Tolkein made alterations to one chapter of one book to get things back in place. Obviously he never suppressed the publication of books which highlighted the changes either. And his alterations were in keeping with the original, to avoid the necessity for further changes.
Lucas, however, has made changes and additions throughout all of the three parts originally released and then brought out three new parts which contained further inconsistencies and so he brought out new versions with even more changes! To further complicate matters his changes have been made in a lacklustre fashion, diminishing the works from their original potency!
This makes it fairly obvious that Tolkein had a very carefully imagined world and mythology from which he created his works. Lucas has made an increasingly jumbled, ill-thought-out series of films from which it is difficult to grasp a clear picture of the worlds and mythology they are 'based' on.
[Sigh]