Panettone: what does "American variant" mean in the recipe

Useful to know

King Arthur explicitly presents American-Style Panettone as a version of the sweet festive bread. It includes a biga preferment, eggs, butter and a selected dried-fruit mixture. [1]

It should not be presented as the only traditional Milanese method. The source allows different shapes, including a ring rather than just the familiar tall cylinder. Follow the quantities and vessel for the chosen version. Add the fruit at the specified stage instead of kneading it indefinitely in pursuit of even distribution.