Actually it makes their point. Linux is super widely used, meaning it has millions of eyes on its codebase and it's a very high value target for both attackers

Actually it makes their point. Linux is super widely used, meaning it has millions of eyes on its codebase and it's a very high value target for both attackers and security researchers. OpenBSD is just a LOT less used, meaning that there might be latent security problems that no one bothered to uncover. It's very easy to have less CVEs when you are used less, that's why I have some doubt about the "secure" reputation it has.