I'm not sure what that branch is about. Yes, I suppose it could be an external fuel pump connector but where is the pump? They are handy, work well, and have a long lifetime. Even if the tank pump is good, and external doesn't interfere so if it was for an external, why isn't it still there? Unless the PO wanted to keep it for himself.
Are you sure that the connector was put in by the PO? Not the factory?