This is one of the best explanations of the xz matter I have seen so far:
https://lcamtuf.substack.com/p/technologist-vs-spy-the-xz-backdoor
and it leads in with a quote to remember -
"This dependency existed not because of a deliberate design decisionby the developers of OpenSSH, but because of a kludge added by some Linux distributions to integrate the tool with the operating system’s newfangled orchestration service, systemd."
Enjoy!