The GPS switch-on sequence was included in the after start procedures; in 2 aircraft it was a GNC250 and was part of COM2 and on the other 2 it was a standalone GPS150. None of the aircraft had moving map GPS, so the basic information was position plus bearing/range from home aerodrome.
Students have to learn to walk before they can run, peter. The GPS systems were not 'moving map' and it was mandatory for students to learn the basics first - which they were also required to demonstrate during the PPL Skill Test.
If a student knew how to use the GPS correctly to navigate to a diversion, I would allow them to do so on the PPL Skill Test after first estimating heading and distance conventonally. It boosted their confidence considerably when they found how accurate their estimates were.
Remember that we train and test for a generic class rating and that not all rental wreckage has GPS. But they all have windows out of which to look and methods of assessing heading and time!