Question on Enabling Kerberos Authentication using SetSPN for Availability Listener alternative DNS name
Yes, a SPN is simply telling the client that when it connects to the specified service (MSSQLSvc) on the specified host (shortername.mydomain.com), the specified principal (MYDOMAIN\SQLSvcAccount) will be the owner of the process that it is connecting to.  This ensures that the connection will fail if DNS is wrong and it ends up connecting to a process owned by a different principal.