What is the scholars' evidence for excluding the noon-time shadow (fay' al-zawwal) in determining the end time of Dhuhr, even though the hadiths mention "the shadow of everything being its like" without exception?

The scholars are of the opinion that the remainder of the shadow upon which the sun has passed is not counted as part of the Dhuhr time. This varies according to different countries and seasons of the year, and sometimes no shadow remains at the time of zawal (midday). The Dhuhr time begins with the zawal of the sun, which is when the shadow stops decreasing and then starts to increase, even slightly. The Dhuhr time continues until the shadow of everything becomes equal to its length, in addition to the shadow that was present at the time of zawal.