The book's table of contents is a dead giveaway. You'll usually see 'The First Christmas' as Chapter 1, then maybe 'The Legend of St. Nicholas,' then a bunch of unrelated winter tales. This shows the attempted lineage: from the historical/religious event, to the saintly figure that inspired Santa, to the purely imaginative stories. It's a direct attempt to create a narrative bridge, suggesting Santa is a folkloric evolution of St. Nicholas, who was inspired by Christian charity. Whether that historical simplification is accurate is debatable, but the book uses it as a structural blending mechanism.