Depends what you mean by navigation. A watch is a very competent device to follow a predetermined course. I've used dedicated GPS units, smartphones and watches and in my experience a watch is as good if not better than larger devices when biking (more so when hiking because you don't have to fish the device from your pocket, less so when boating where map layers are often critical).

It you mean course design, you are absolutely right. Pre tour, I try to generate courses on a computer. On tour, from a phone. From a watch would be excellent training to develop patience.