Why are you calling it Chinese controlled Tibet or the Himalayas? The river as provided in your image literally flows from China into the disputed regions. The rivers don’t start in the disputed areas. That is China not Chinese Controlled Land. Do we call corn from the America as US controlled Ohio or their tech products as US controlled California?
No, he is correct, if using an Oxford comma, it would be like this:
"Chinese controlled portions of the Himalayas", and Tibet
The Himalayas spans multiple countries, so what is the issue?
A more apt comparison would be the Canadian Rockies and American Rockies