Yes, as long as there is no new ETS application file published for the firmware update, it does not need to be updated. In this case, the ETS configuration is retained during an update. This is mainly the case with smaller updates (e.g. V3.6.2 to V3.6.3).
If a new firmware and a new ETS application file were published for the update, then both files must be updated. However, this will overwrite the ETS configuration on the unit.