Even with a mobile app, it may still be worth knowing how to navigate the old fashioned way. I would imagine that books / hand calculations are more resistant to power failure than apps and GPS are.
The military is quick to embrace new technology but slow to completely rely on it to the exclusion of other methods. The great fear is that technology will let you down at a critical moment via failure or damage. That's why they teach the old methods alongside the new ones.
One time we bolted some backpack straps to one, painted it camo, and called it our Tactical Teletype. The joke was that it was 350 pounds of steel parts and electric motor...
How long you spend on the topic and whether you have to prove proficiency is a different question.