Yeah I remember him talking about it on stream and he said that the update would take around 9 months to finish.
Right, but he didn't realize all that was involved with the update and really didn't have a complete vision of what he wanted to accomplish at the start.
Also, there's the 90-90 rule in software development.
Let's also not forget Hofstadter's law.
In addition, every pre-tech update was written for code to fit first in the old code and then it has to make sure it fits in the new updated code that is to come out - so every pre-tech update added more time to the tech update for posing and coding (I assume DC made the art for 16:9 to go in the new version and cropped what he needed for the current version).
And once you get underway making updates and revisions, you find things that you would like to implement and decide not to put them off to a future revision. While you're in there now, you might as well get it done up front.