The external sd file within the phones sd folder is the link to the external sd card. Putting files in the external sd folder does not fill up the phones internal sd memory.
You may need some game files to be within phone sd for faster access but there should be an option in the game settings to save content files to the external sd.
Edit: Just checked and I have Gameloft's MC3.
If you go to Settings > applications > find your game and select.
You should have the option to move to sd - that is the external sd card.