Users with low vision adjust font sizes to the minimum size needed for comfortable reading. Many users with low vision do not use assistive technology, but rather adjust to the largest font size supported by the user agent.  Reducing the size of the font - particularly a text-dense element like "article" - increases the imbalance between font sizes in other parts of the page (e.g. the user would be forced to increase font size for the article text to the point where the font size in the non-nested parts of the page are enlarged so much as to overflow their containers. Automatic reduction of the size is unnecessary and will decrease access for users with low vision.

Proposal: Remove the section. Nested elements should not have the containing text size reduced automatically.  The author can choose to reduce the size of nested text through CSS, but it should not happen to font sizes automatically.