And I agree. My observation have been the same. It doesn’t make sense. My drive for most of the last 10 years was the continuation of yours, from Carmel Valley to La Jolla. Though I rarely hit any morning traffic, only a little slowing just north of Genessee. Evening traffic varies based on time of year, but slows usually somewhere between the merge and Del Mar Heights Rd. (Except for Fridays, which are totally unpredictable, sometimes nothing, sometimes extra heavy.)
But I look out my office window and see the southbound traffic getting very heavy as early as 3:30 and I know it’s that way all the way up to Oceanside some days. I have no idea why there isn’t any corresponding morning traffic going northbound.