The part the author is missing is that Box and Uber have already claimed the code as their own. It will be in the employment contract. The author appears to be under the impression that asking a mid-level manager (or even a senior manager) "Hey, do you want this?" and that manager answering "No", is in any way legally binding on the company.
I've only ever agreed to those terms kicking and screaming. I wish there was a larger part of the community willing to advocate for a "love of the art" clause that would explicitly state that code I wrote on my own time is mine.
