The program works by using the save-load method and simply observes what the game offers. Hasn't anyone, in all these years, managed to extract this skill tree directly from the game's code?

If it hasn't been discovered yet, it might not be stored; most likely, the game uses a pseudo-random number generator internally, and the current state of the game (positions of objects on the map, current resource amounts, the hero's army) is used to determine the next random number, and some sufficiently complex transformation is calculated. For example, if something is changed on the map or in the battle, the morale that worked in the previous load will no longer work, but if all the arrangements are copied exactly, the morale will repeat.

Determining exactly which transformations are performed and what is used in the pseudo-random number generator is quite difficult; it requires serious reverse engineering. In this case, save-load is much simpler.