The abrupt change in time-of-day when commits occurred supports the theory that Jai Tan is more than one person: https://twitter.com/birchb0y/status/1773871381890924872
At that point it would have been clear “the race is on” to avoid detection, so it’s not too surprising someone would work late to salvage the operation.
Out of interest I looked up the other commit at that time of day visible in that graph, laying on the arrow. It's [1], which changes the git URL from git.tukaani.org to github.com. Of course, moving the project hosting to github was part of the attack.
[1] https://git.tukaani.org/?p=xz.git;a=commitdiff;h=e1b1a9d6370...