That hypothesis privileges spells with either intelligence, or at least analytical capabilities, as if some sentience drives them. We create a spell meant to "heal", but heal is a vague term. There are no specifics there, and therefore either it acts mechanistically or there is some overarching analytical power that either comprehends for us, or predicts possibilities and comprehends them enough to choose the best manifestation of power.

The question then is, if spells are driven entirely by intention, then we can use them to fucking ruin the world. For example: I cast a spell with the intent to write out every single law of the universe in easy-to-understand mathematics. If spells are run by our own comprehension, this is impossible, but if it is run by intent as arbitrated by a higher power, it will produce exactly what I want, and that will rape this setting hard. Please don't give me that power.