We have already discussed the blatant, intentional, and obvious own-will in violating one's own mechanics. I will write it once more: nobody likes that. But you are wrong about "not needing much effort." It only seems that way to you until you run an exp yourself. A Mage Guild is not a robot to keep such a large number of rules in mind, even if he wrote them himself. Even games created by hundreds of well-paid WORKers lag, bug out, and ruin the walkthrough for players. In the last exp, for example, I simply forgot about one rather important combat mechanic. It didn't strongly affect the game because I forgot it for everyone, both players and NPCs, but there is your example. And if it had only negatively affected the players, you would most likely have been very dissatisfied. Moreover, sometimes rules arise during the game when a player wants something that wasn same initially thought through, and thinking everything through is nonsense—it's impossible. Such rules are also the own-will of the Mage Guild. Whatever he says, goes.
Ничто не возникает из ничего и ничто не пропадает бесследно.
Если где-то чего-то убудет, то в другом месте добавится.
(Закон сохранения).