The packs’ own body text is around 14–17px with about 1.5 line spacing. That suits English docs, but it feels cramped for long Korean health articles. So these values are fixed above the pack, and a pack cannot shrink body text to be denser.
Four things are fixed: body size (17px on phones, 18px from 768px up), line spacing 1.8, word-level line breaks (keep-all), and tap targets of 44px or more. Measuring the list text in the demo gives 17px with 30.6px lines, and the product-list button is 48px tall. Sizes of titles and of UI parts such as descriptions and button labels come from the pack; the reading rule applies only to body text.
No automated check measures this directly. It holds because the values are fixed above the pack, so a pack cannot set body size.
When to use
Think of it when building a new pack, or when one pack feels too dense. Do not shrink the text to tune density; use spacing and rules instead.