For many years I ranted vociferously about this "injustice". Indeed I used to get wound up by this quite badly.
His may sound a bit far fetched, but as I understand it, the reason is that the south stand (Park Lane End) goalmouth, only actually gets full natural sunlight for a few days per year. In fact I believe it is around the longest day time that this happens. This is because of the tightness of the ground, combined with the height of the stands. Our groundsman claims he therefore needs an extra week or so to get the pitch into the pristine condition he PL rules demand, hence our request.
It is also my understanding that due to the number of complaints the club has received over the years about his fixture "bias", that they asked the stadium tour guides to mention this in their commentary on the tours.