Well, look at it. The high is powering the low when the highs are on, so the grey is on the high end. The lows are powering the fogs when the lows are on, so the grey is on the low end.
Done the opposite way as you suggest, the lows would come on with the fogs. If you're using fogs, your lows are probably on anyway due to the sensor. So it is redundant. However, this results in what I was trying to avoid, which is the need to turn the fogs on at start up every time. With my setup, when my lows are on, my fogs are on. When highs are on, lows are on, thus fogs are on.
Done the opposite way as you suggest, the lows would come on with the fogs. If you're using fogs, your lows are probably on anyway due to the sensor. So it is redundant. However, this results in what I was trying to avoid, which is the need to turn the fogs on at start up every time. With my setup, when my lows are on, my fogs are on. When highs are on, lows are on, thus fogs are on.