Not a developer but reading the changelogs and commit history from this person seem interesting, as they appear to be some effort consolidate control and push things in the direction of supporting wider dissemination of their backdoor code:

Discussing commits that the other author has since reverted, IFUNC change with Project Zero tests, a focus on embedded, etc.:

https://www.mail-archive.com/[email protected]/msg00642.h...

Trimming security reporting details:

https://git.tukaani.org/?p=xz.git;a=commitdiff;h=af071ef7702...