It will indeed by default add them in duplicates, since it can't know you are speaking about the same game.
You can however link multiple imported games to the same game in your collection by using the overflow menu (the 3dot) on the game line in your import screen. This is what I do for all import resources.
I never really thought about this, but I could auto link multiple games (if title & platform is the same), I have the impression that you expected the app to do this already, correct?
The online database usually uses the official name of the game, some source are using different names for some games. I'm working on adding xbox import at the moment, and it's the worst I have seen so far ...
For games that can't be auto matched you can use the manually link. Clicking this option will search the Online database and ask you which one it is. This added game will then be linked to the game from the import source.
More information:
http://www.tuyware.com/index.php/my-game-collection-2-0-help-import/The playstore character limit is really annoying, and way to short if you want to do more then a 'mail me' message :/ I'm interested to know which options you would need extra to have MGC as your main collecting app? If it is settings you miss, then we did a poor job providing them. Any ideas around this are welcomed.