Not a legal expert, but suffice to say it's not without it's challenges. In practice, as a hiring manager, I've had the luck that it hadn't made a difference either way since I always had some promising URMs in the pipeline. (Edit: I take that back. At one point I had 4 reqs and the first candidate was a real unicorn and we hadn't interviewed a URM yet. My VP gave me an exemption on the condition that the other three reqs have to go the proper route. I got the exemption because he knew for a long time and trusted me and because of the remaining, identical reqs)

Edit: To some degree it's a variation of the same old goals/metrics spiel. Ideally you'd have managers who want to give URMs a chance. In practice creating this metric to force it makes nothing better but likely everything worse for everyone in the system.