its hard to disorientate when you have those massive rocks sticking out like a saw thumb on the horizon
As A380-800 Driver points out, it is not hard but the rocks are. Disorentation is not restricted to spatial disorientation in IMC. I've seen many a good pilot disoriented (suffering from illusions) 'in the clear' but without a visual horizon....even though they thought they had one.
PNG and Irian Jaya seem to be the worst places I've witnessed it happening.