If I remember, fingerprint was verified using libssh2, but I do not think they do SHA256 yet. Tried to look in their documentation but didn't find it. Would be a great addition too.
Right now it seems to show an SHA1 hash encoded in hex, which is very inconvenient because ssh-keygen displays either MD5 in hex or SHA256 in base64. It should at least tell the user what hash algo was used, I found that out by trial and error.
