I love your Strava map! That's hilarious. Definitely the Garmin for accuracy. Thanks for posting. I head up next week.
Actually, Chad, Garmin GPSs do that too. Notice how smooth things are at the summit, compared to Trail Camp. That's because gps technology depends on lots of satellites being in view, and if you are in a valley with high mountains around, gps accuracy is terrible.
I tried to map a course on the North Fork Line Pine Creek -- the Mountaineers Route approach, and the track looked like his route between Trail Camp and Trail Crest.