Why is the Karambar Pass considered a possible eastern boundary of the Hindu Kush?

The Karambar Pass (14,250 feet [4,343 metres]) is tentatively accepted as the eastern boundary of the Hindu Kush because the region's locally complex topography makes determining a precise eastern limit difficult.1

Geographically, the pass serves as a marker between the valleys of the Konar (or Chitral) and Gilgit rivers. It also functions as a starting point for the eastern section of the mountain range, which extends from the Karambar Pass to the Dorāh Pass. While some authorities view the Hindu Kush as a continuation of the Karakoram Range, the Karambar Pass remains a significant, albeit tentative, point of demarcation for the range's eastern extent.123