IMHO, It should break the CI systems.

If you don't pre-bake the known-hosts, then you'd allow each new ephemeral run to use whatever github tells you it's key is.

It did briefly break ours, as we pre-bake the known_hosts file into our CI image for convenience and security.

Convenience due to CI not having TTY's, so various tools would get stuck on prompt Y when connecting to github for the first time. (Which is every run, if you are ephemeral CI)

And security, as now everything broke due to github's key changing, which is the desired outcome actually.

We bumped the known_host key entry, merged and all is well again...