It was just an example. It used to be fairly common for people to sync some of their dotfiles via git, and from time to time someone would leak a directory that contained sensitive data without them realizing it. I'd guess things like tokens used by cli tools were more common than whole .ssh directories, but I'm sure both happened.

Not quite the same thing, but also a leak: https://blog.gitguardian.com/github-exposed-private-ssh-key/

I guess all these folks saying professionals would never make a mistake like this will also have insulting names for github engineers. :shrug