That makes sense, I think. If it treats Tabula Rasa as print_default_stylesheet, the Modish CSS as print_stylesheet, and then the color themes for Modish as print_theme_stylesheet, using print_styleshet in a Modish theme layer would (and does) override all the Modish CSS and leave you with a themed Tabula Rasa. Since Skittlish Dreams isn't a child of Tabula Rasa, print_default_stylesheet is the Skittlish CSS, so print_stylesheet doesn't override anything.