It depends on the HR department. Some are under pressure to "add value" to hiring, so they insist on rewriting job reqs and screening all applicants. At a Fortune 50 company I worked at, my boss got in trouble because he sweet-talked someone in HR to print out all the resumes they rejected and secretly deliver them to him. He resorted to this after he informally recruited a new hire, wrote a job description specifically targeted at them, and then, after waiting two weeks for their application to filter through the system, found out that HR round-filed it because they supposedly weren't qualified.
HR refused to collaborate with him on editing job descriptions, so every time he submitted one, he had to check every day until he found out what garbage they posted so he could go beg them to fix it. They would randomly add technologies and "change the wording" of desired qualifications (how do you "change the wording" of proper nouns and jargon from somebody else's field?) and they were especially fond of turning nice-to-haves into absolute requirements because we supposedly didn't have enough. My boss was convinced they were under pressure to filter out a target percentage of applicants, because he begged them to just pass all the resumes to him, and they refused, hence his cloak-and-dagger tactics to get his hands on them.