This issue occurs because the login banner is not encrypted. According to the Secure Shell (SSH) standard, there must be no information passed until the client has connected and the session encryption keys have been exchanged.
This problem is identified by the Cisco bug ID CSCdu13747.
The login banner is in unencrypted form and is not supported in the SSH version. Since any unencrypted text cannot be sent before logon, the banner does not appear when the switch is accessed through SSH.