A company's hiring practice should reflect the type of engineer they want to hire. If they want to hire engineers that can start contributing immediately, and they hire engineers that need mentoring, then the hiring process is broken.

If they widen their expectations, and hire people that they believe they can mentor into net contributors, then their hiring practices should reflect this.

There are many ways a company can make hiring more scientific, including A/B testing (ie. hiring people they normally wouldn't, have more data around how productive new hires are, etc) but I've never seen it over than "copy Google and we should be good."