Why don't foreigners enter the only tourist attraction in China where foreigners are not allowed to enter?

The Jinkou Grand Canyon of Dadu River is about 26 kilometers long, and the whole canyon spans Hanyuan County of Ya 'an City, Sichuan Province, Ganluo County of Liangshan Prefecture and Jinkou River of Leshan City. The valley of Jinkou Grand Canyon is about 600 meters above sea level, and the average height of ridges on both sides of the canyon is about 2600 meters. Jinkou Grand Canyon in Dadu River is the longest, most dangerous, narrowest, deepest, most male, most tidy and most secluded canyon in Sichuan, which is really rare.