How does ssh ignore the redirect and write anyways to the console?

.ssh.exe [email protected] -p 1022 -v > test.log 2>&1

Output shown on windows console (perhaps the same under linux?):

The authenticity of host '[127.0.0.1]:1022 ([127.0.0.1]:1022)' can't be established.
ED25519 key fingerprint is SHA256:xeS1I/8fteLkGqn43X0VkBpBgY7IIAo9Ysy69r/8iHQ.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])?

I know, the message is for interactive interaction and thus does not makes sense to be redirected, but how does that work? Any code references?