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It looks like your right. They apparently have a "reveal this product" option on each game. If it isn't revealed you trade it with all keys but if it is revealed it then shows "reveal key" options on each platform it may have keys for and they can then be set to trade-able individually. I didn't use the trade system very often and didn't notice. Not sure if it should be conducted that way but it is. Thanks for your help, looks like I was mislead.