The geometry of typography
Body type, the unsung middle of every screen reading experience, owes its hierarchy to scale. When a sliver of a per-cent moves, every paragraph, caption, table row and footnote moves with it. text-size-adjust as a multiplier means that a single declaration retunes the entire flow.
The new model is: pick a base in the cascade, then declare the adjust. No conditional-load polyfills, no mobile-only hacks. The whole article — body text, code spans, even nested lists — recomputes.