IANAL (and certainly have not read the text of the law), but "reasonable" sounds fairly easy to game in many situations. "Your honor, our job listing made things quite clear. If qualified candidates were scarce, we could go as low as 1/4 time. Or if a candidate who was highly over-qualified wanted to get a foot in the door with us, to then apply internally for a higher position when one opened up, his or her starting salary could reflect his over-qualification...".

(Note that they already seem to be getting away with the "overly burdensome" argument. The plausibility standards applied to legal arguments made on behalf of large corporations are, ah, minimal.)