From that I ended up getting
"local harvesting" = sending private key of [Account A ] to server.
"delegated harvesting" = sending private key [Account B ] to server.
The fee you explained is the result of the passing of the private key to the nis server. I'm guessing

Local harvesting = send the private key of the account you are harvesting with to your local NIS.
Delegated harvesting = a new account is generated with zero balance, but importance score of the account for which you activated delegated harvesting. then the private key of that new account is sent to (any) NIS. the harvested fees still go directly to the original account (for which you activated delegated harvesting).