Why is there no mention of chromatic aberration? I understand that blue makes a good background because usually in a normal human eye blue will be defocused.

Why is there no mention of chromatic aberration? I understand that blue makes a good background because usually in a normal human eye blue will be defocused. https://www.nature.com/articles/s41598-020-79911-w https://www.nature.com/articles/s41598-020-79911-w