You should probably point out that the reported FT

You should probably point out that the reported FTD numbers reflect aggregate fails as of a specific point in time. So the FTD's outstanding as of 12/21 could have been from transactions on the 19th, plus any previous outstanding FTD's. Also, fails can occur on sales marked long as well as short.

See the info below that was gleaned from the link you provided:
https://www.sec.gov/data/foiadocsfailsdatahtm

"...Fails to deliver on a given day are a cumulative number of all fails outstanding until that day, plus new fails that occur that day, less fails that settle that day. The figure is not a daily amount of fails, but a combined figure that includes both new fails on the reporting day as well as existing fails. In other words, these numbers reflect aggregate fails as of a specific point in time, and may have little or no relationship to yesterday's aggregate fails. Thus, it is important to note that the age of fails cannot be determined by looking at these numbers. In addition, the underlying source(s) of the fails-to-deliver shares is not necessarily the same as the underlying source(s) of the fails-to-deliver shares reported the day prior or the day after."

"...Please note that fails-to-deliver can occur for a number of reasons on both long and short sales. Therefore, fails-to-deliver are not necessarily the result of short selling, and are not evidence of abusive short selling or “naked” short selling."