They say "an open-source developer requests to remove the dependency that links xz to OpenSSH" while showing https://github.com/systemd/systemd/pull/31550 on screen, zoomed and focused so the word "systemd" does not appear.

They never once utter the word "systemd", anywhere in the script... isn't that strange for such a key dependency?

It probably is because of video length, mentioning systemd would mean explaining init system which could add another 5 min runtime. At least they showed it in diagram of dependencies.