Is a thermometer in the egg box itself necessary?

I have a professional made incubator. I have the egg box, thermostat probe, and accurate thermometer all on the same level in the incubator, not that it matters anyway as I don't seem to have any hotspots. the incubator and eggbox will be the same temperature, no need to put anything in the eggbox itself, Right?

If you have proven to your own satisfaction that the temperatures in the egg box match what is outside the egg box, then you only need one thermometer, and it can be anywhere you want. But the egg box temperature is the important one. If the thermometer is inside the egg box and the temperature is right, you do not need to make temperature comparisons between inside the egg box and outside the egg box.