It's an artefact of OpenSSH braindamage, like a WiFi device spraying probe requests OpenSSH sprays all of your keys to any server it connects to and then takes

It's an artefact of OpenSSH braindamage, like a WiFi device spraying probe requests OpenSSH sprays all of your keys to any server it connects to and then takes whatever the server responds with as the one to auth. There's a CVE for this, CVE-2016-20012, but the OpenSSH maintainers rejected it as by-design, https://github.com/openssh/openssh-portable/pull/270 https://github.com/openssh/openssh-portable/pull/270.