I wondered about this. I saw the note at the bottom "RedHat announces that the backdoored xz shipped in Fedora Rawhide and Fedora Linux 40 beta" but saw nothing in the timeline explaining when/how it made it into Fedora.
https://lists.fedoraproject.org/archives/list/devel@lists.fe... (https://archive.ph/diGNB)
This is the rough sequence of events in Fedora:
https://lists.fedoraproject.org/archives/list/devel@lists.fe... (https://archive.ph/e0SdX)