If you read the description that comes when you try to infuse, in order to infuse you must have another of the same type of gear in your inventory, the item must be unlocked and have a higher defense, AND be from the same year.
Basically since there is only the bland ghost and the frontier ghost from year one, there is no way to infuse the frontier shell, making it pointless to be infused
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Exactly. That's why I was wondering why it had it in the first place if it is ultimately useless.