Is there a difference between the final rinse water temperature and the dish surface temperature?

Answer (from ThermoWorks)

Yes, the final rinse water sprayed from the spray arm nozzles cools as it sprays onto the dishware. Most commercial dishwashers heat the final rinse water to around 190°F as measured by the dish machine’s dial gauge or digital readout. Water at the dish level will typically be 10-15 degrees cooler. Most restaurants don’t calibrate the dish machine’s readout and rely on the gauge, which can drift over time causing the actual temperature at the spray nozzles to be much lower. DishTemp is calibrated and includes a NIST-traceable certificate and is the best, most accurate way to validate temperature at the dish level.