Is the person already lean? How intense are his workouts? What are his goals? Has he been primal/paleo for a long time?
I ask because the diet you describe will never give the person a chance to switch over from sugar-burning to fat-burning metabolism. For most, this translates to inability to reach maximum leanness.
As for health, more carbs in the diet means more insulin in the blood, which means more risk of heart disease, higher blood pressure, and a host of other problems.
What would be the motivation for choosing a diet such as you describe? All I can think of is lack of commitment or, possibly, something based on the needs of a competative athlete.