@Con-Hennekens thanks for taking a look. Your observations could well be correct - being as this was my first 'real' test of MyRoute-app navigation, I had a Garmin XT as backup, and in order for it to follow the route, I needed to make sure I had enough via points for the XT so it would stick to the route.
Yes, very interesting routes we had on this trip - this was only 1 of 3 that was very full of Appalacian Mountain curves/elevation changes - this was perhaps the route with the fewest changes, believe it or not!