That's not a chart for the end of January release. That's a chart for the work determined needed to complete the entire tech update.
Art has been at 98-99% for more than 2 years of the tech update development. It's been waiting on everything else.
Remember, that's based upon the tech update task list --- which Debbie's rework was not originally going to be part of the tech update. But partially because everything else is taking along time, as well as other reasons, DC decided to take this time to do Debbie's rework -- but that's not reflected in the data used to calculate the chart.
Someone has tracked all the points over the years and posted graphs in the past. Also, if you're really curious, you could always use the Internet Archive's Wayback Machine to look at the history of that page
You must be registered to see the links
and the chart.