Does one plan a series of diversionary alternates when crossing the rocky mountains? Of course not.
When overflying The Himalayas? Not necessary.
As I said, the Himalayas/Tien Shan mountains are far more extensive and much higher than you expect. You can't just turn off the airway and descend (and lose your MSA protection). Escape routes towards nominated alternates are planned from waypoints en route leading you to lower MSAs. These mountains are in a very different league compared with what we know!