Not according to Rossi's testimony. And in any case a few fins would not help. You are not surprised because you have not tried to work out how you could get the claimed 1MW from the 200m of piping Rossi swore he used.
Did Rossi deny using finned radiators? I admit it is my speculation only, but I don't think he has ever denied using them, and he has been known to use them with past configurations. Why would he all of the sudden stop using them in this instance?