It is hard to take any stylesheet seriously when their website doesn't even properly use meta color scheme tags. Also, their examples are like the opposite of normal element approaches to what you're trying to accomplish. for quote attribution? How does that even make sense?
> Attribution for the quotation, if any, must be placed outside the blockquote element.
… and suggest things like `blockquote + p` and `figure > blockquote + figcaption` instead. I will also note that that use of figure would have been semantically inappropriate a decade ago, when figure was supposed to be something that could reasonably be taken out of the document flow, but now that’s been downgraded to just being a self-contained unit, though it may be able to be taken by itself and it’s generally suggested that you refer to figures by their captions.