SSH helps keep us secure in many ways, one of those is the host-key fingerprint which is unique. If you have been connecting to an SSH server that you've made no changes to and suddenly ssh warns that the key doesn't match then you have a problem.
But how about connecting to an existing server for the first time on a new machine or client?
A lot of new clients calculate it using an SHA256 hash but it is not as easy on your host machine to produce the sam........