I think you might be overestimating the consistency and reliability of how hiring is done. (For reference, I've worked as a hiring manager of software engineers

I think you might be overestimating the consistency and reliability of how hiring is done. (For reference, I've worked as a hiring manager of software engineers for a few years.) I've seen departments just use the same description over and over for years, and share it between teams -- even when it's not even really correct at some point. Practices vary wildly between company, and even between hiring managers.