If you're exposing the photo properly, I don't see how ISO 200 would yield any better shadow detail than ISO 100 (that's assuming that you're adjusting your aperture or shutter speed 1 stop to compensate for the increased ISO). On the other hand, if the higher ISO is being used to ETTR and the shutter speed and aperture are not being used to fully compensate for the higher ISO, then I think there is validity to the idea of maintaining better shadow detail. When in bright sun, it's often possible to ETTR by adjusting either aperture or shutter speed without the need to boost ISO. From my understanding, simply shooting at a higher ISO and compensating with the aperture or shutter speed is not going to yield any better shadow results. Thoughts?