The hardest thing for a student pilot about dead reckoning is not spotting features, roads and rivers per se, but the workload that comes with it.
If you let the GPS take that pressure away from the pilot, you are making the exercise much easier, which defeats the purpose of getting someone used to cockpit management/multitasking.
After all, multitasking is the most difficult thing about flying, if you take that away what's the point ?