"Secondly, the author doesn't make a convincing argument that the fact that the reason why men get all the risk and all the reward is because of something innate, instead of a self-perpetuating social system that actively encourages one gender to risk it all and reap the rewards, while holding back the other gender to mediocrity and risk-free existences. The possibility is raised for a few sentences, and discarded, as if it's ridiculous, and it's obvious that the reasons are inherent."
The article explains that the "innate" reason is simply that, biologically speaking, men are more expendable. A few men and many women can create a large population more quickly than many men and only a few women. Applying risk equally possibly results in a substantially reduced population, while leaving risk mostly to males allows more to be accomplished without strongly affecting population numbers. Great rewards provided for those who succeed in a risky endeavor merely supports the accomplishment of those objectives. I'm not sure where you find fault with this argument.
The premise is undeniable and the only conclusion that is on even possibly shaky grounds is that societies would act to preserve their population, hence leaving men responsible for risky activities. To suggest otherwise does seem "ridiculous," though I'd love to hear someone who disagrees with that and why one would believe otherwise.