According to wikipedia, you are right, I don't mean cache. I hadn't been aware that I was misusing that term, and will try to avoid doing so in future - thanks for that! - though now I need a word to describe what ssh is doing.
In fairness to ssh, as I demonstrated above, it is doing exactly what you asked it to: putting up a message when it associates a new IP address with a known host name. But I agree the message could be more helpful.
I think this thread is rather separating those like ballombe, who do want to know when the IP of a server offering a service they use changes, from those who don't, like yourself.
I've found this thread most stimulating, and I now find myself having to sit down and think harder about what I want from an authentication service in a world where DNS is not trustworthy.