Pure speculation, but I would think the changes to muscle recruitment caused by raising or lowering a saddle could cause the need for saddle set-back adjustment. Further speculation would be that for different people, and with different saddle height starting points, you would see different necessary adjustments to saddle setback. So, for one person raising the saddle might result in a need to increase setback, for another it might result in a need to do nothing or decrease setback, all because of different saddle height starting points and different body development.

Of course, speculation is cheap.