Having never heard of Lynn Stout, her claim to fame on Wikipedia is that Supreme Court Justice John Paul Stevens cited her work in Citizens United v Federal Exchange Commission... in the dissent.
I could believe that oxygen doesn't exist, and I could probably find somebody else to agree with that, perhaps even an author or something, but if there exists a body of law that is on the books and that will punish you for violating it, the idea of shareholder primacy is very much not a myth.
Dodge v. Ford 1953:
> The Court held that a business corporation is organized primarily for the profit
> of the stockholders, as opposed to the community or its employees. The discretion
> of the directors is to be exercised in the choice of means to attain that end, and
> does not extend to the reduction of profits or the nondistribution of profits among
> stockholders in order to benefit the public, making the profits of the stockholders
> incidental thereto.
This all extends on precedent set way back in 1896 (though there may be earlier) in Steinway v Steinway & Sons, though in the case of Steinway, the philanthropic behavior was excused as having had pecuniary value. It's been cited since, and punishments are being levied in spite of the myth. While it may be true that there is no law codified to speak expressly on the duties of shareholder primacy, stare decisis specifically disagrees with that, and that's really all that matters.
In the real world, of course there is no duty to maximize value at all costs, and the board elects a CEO who will do a good job of balancing short-term value against long-term value, and while actions such as Cook's are likely debatable either way, if we took a more extreme example, and Cook were to give 80% of Apple's assets away to charity, he would very certainly be sued, and he would very certainly lose. If, as in Steinway, the charitable actions could be argued to lead to longer term profits, the case gets blurrier, but the idea that shareholder primacy is a myth that does not exist is simply too unqualified a statement, and too counter to the facts to be regarded with much weight.