I believe the map naming flexibility on the newer units applies whether the map is placed in internal memory or micro SD card, as long as you put the file in the Map folder. I don't have one of these newer units to test with, so someone please correct me if this is wrong."
I tested your Map folder statement on my 2460LMT and it seems incorrect. A MAP folder on the Nuvi itself WILL NOT BE RECOGNIZED (at least on my 2460).
I created a folder named "Map" in the Garmin
folder and copied a map named gmapsupp.img in it.
The map was not recognized.
I then moved the Map folder(with map) into the system
folder, the 2460 did not recognize it.