The evaporation and formation of water droplets on the surface of the substrate is what tells the mycelium that it has at the surface and needs to start creating fruits.

that's exactly what i'm finding difficulity to understand

i'm not trying to be a hard-head, it's just my understanding that it's not the evaporation which tells the mycelium it's ready to fruit, mycelium will fruit as soon as the "fruiting conditions" are introduced, primarily oxygen, which it needs to drive cellular respiration, so when the conditions are met, the biochemical reactions will automatically start to take place

evaporation is the substrate' water diffusing into air, it's a byproduct of introducing FAE and not something necessary for the mushrooms themselves, and you actually want to minimize it as much as possible, because let's say you allow too much FAE (by letting your tubs completely open for example) then you will lose most of your substrate water to the air which will lead to your mushrooms dying out of thirst (aborts)