Can I ask for why it wouldn't have been discovered if the obvious delay wasn't present? Wouldn't anyone profiling a running sshd (which I have to imagine someone out there is doing) see it spending all its crypto time in liblzma?
The situation certainly wouldn't be helped by the fact that this exploit targeted the systemd integration used by Debian and Red Hat. OpenSSH developers aren't likely to run that since they already rejected that patch for the increased attack surface. Hard to argue against, in retrospect. The attack also avoids activation under those conditions a profiler or debugger would run under.
