I doubt that any Calorie calculation would take that into account. If power data is used, it is just translating total amount of work in kJ to a total amount of energie from food in kcalorie. This uses the Joule to calorie factor and the efficiency number that you also mentioned.
At a certain point there is not much benefit in getting more accuracy. There are probably many more factors that play a role in the efficiency value, like differences from person to person, outside temperature, types of food...