Having a hiring manager intake is about turning wish lists into unbiased requirements. It's about hiring the right person.
Hiring managers shouldn't write job posts. If you as a recruiter don't know how to write a job post - how would they?
Do you know how to delete biased requirements from your job postings? It starts with this question during the hiring manager intake.
If you ask better questions during the hiring manager intake, it's a lot easier to write a great job posting and hire the right person.