Did you ever confirm this?
I think you are right, the recall added the new coolant lines, coolant level sensor, replacement thermostat, bypass valve, and some odds and ends. The programming added ECU logic to protect the cylinder head in case of low coolant levels and additional warning messages on the dash.
The newer cars had a different cylinder head design, which probably moved or completely negated the need for the sensor (head temp is probably calculated and not measured directly). Try to get the newer factory calibrations flashed to your old ECU if possible to confirm thing are working as expected.