Here is the conclusion:
-UseSSL tells the command to use the HTTPS port.
SSL is not an authentication it is a protocol. Kerberos/CredSSP/basic are all authentication protocols. SSL is the transport protocol. Authentication is separate from transport.
Note again that all PowerShell remoting via WSMan is always encrypted even if it is HTTP. Kerberos is always encrypted.
What I should do is, specify the https prefix instead of using the -useSSL switch which will ensure that connection is over https ("https://test.domain.com/PowerShell/);. The -useSSL is meant to be used when you using the -ComputerName parameter.