Reverse engineering (splitting .img with gmaptool) will give strange results when the .img is made from several maps with different TYP files. In the pc Basecamp/Mapsource does not find a TYP file to match the maps and displays an map in a basic way without any typing. Maybe it is possible to solve this in some way if you want to go deep into it...
A simpler workaround if you want the maps in your PC is to download the four maps (links from the index files!) and install them the ususal way. Then you can fine tune the TYP files to suit your gps with typviewer, work with one TYP file and when your satisfied with it just change the map id to suit the other three maps (and rename the files). And then you can generate mapsets of your choise for the gps.