With reference to the touchdown being in a box rather than on a single point, I recall reading that the first ILS systems for autoland were so accurate that they caused runway damage, because heavy jets would always touch down at exactly the same spot on the runway, until finally the runway started to crack at that point. The solution was supposedly to include a random variation in the exact touchdown point that varied within a precisely defined zone, thus spreading the wear and tear around considerably.
Does anyone know if this is true? If I remember correctly, Seattle was mentioned as an airport that had a problem with runway damage from too many touchdowns on exactly the same spot.