(versus in Obsidian - see the .markdown-preview-view portion)
On the latter, .markdown-preview-view.markdown-rendered has .cornell appended to the back of it. This behaviour is not replicated in .print > .markdown-preview-view.markdown-rendered (in the first image).
This is evident in an PDF export of the document:
vs in Obsidian
The PDF export is similar to other documents exported using the Willemstad theme, although the point of the CSS Class is literally to ensure otherwise.