Why do hiring managers input into the design? Would it not be more efficient to have in-house recruiters provide their keyword scan values?

Having been a hiring manager in that space, I'm not convinced the format mattered more than avoiding the obvious overly inscrutable wall of text, grammar check failures, or irrelevant data points.

I agree that not having the issues you mentioned is more important than the resumes format, assuming the format isn't unreadable. We are planning to add functionality to help with content quality.

We work with recruiters and hiring managers to review the designs. The primary things we review are readability/scanability and visual appeal.

We found that a lot of our customers were having more issues with getting offers than getting interviews, so we have chose to focus more on appealing to hiring managers.