Let's define the level. A mathematical proof clarifies an existing equivalence; it does not create it.
The validity of the equivalence between sensitivities based on fixed points and KKT preexists its demonstration, crucial for risk models.
Our investments in Swedish pension funds rely on the discovery of these fundamental relationships, not on their creation.
For example, the relationship between risk and return was not created by modern portfolio theory, but rather elucidated for better strategic allocation.