I remember this, it was the FBI. OpenBSD people did a huge audit and nothing was found. That was also like 20 years ago.
Also, other articles stated that never happened.
Plus, the "backdoor" in OpenSSH was a Linux only thing possibly related to systemd. It never affected OpenBSD. That is because of Linux people patching OpenSSH with "dependency hell". I believe systemd people is doing something about these dependency chains.