I think Dale is right about the pack trail. The photo shows switchbacks 14-26, from about 12,300 ft. to 12,500.The trail is used to access the chute for snow ascents/descents. Bob R. gets back August 13th from his mountain adventures in Arizona and New Mexico, and can give a definitive explanation. I'm interested in hearing about his latest mountain exploits. As far as your question, Brad, I'm among those on the Board who did hike Whitney 30 years ago, and I assure you the switchbacks were the main route back then for summer hikes. Your uncle may have gone up the chute because of late snow conditions, as hikers/climbers do today, when there is a lot of snow.