Grammar used to be taught by notes. ADR-0024 turns grammar points into cards, which means they enter the same review queue as everything else instead of sitting in a separate tab.
The stages built the data contract for highlight spans, rewrote the grammar review, gated the review on having actually viewed the point, and added a minimal intro screen. The highlight-span contract is the part that matters: the card has to mark up which part of the sentence illustrates the grammar point, and that markup has to survive the pipeline that produces the card.
Teaching grammar by card rather than note means the learner reviews it like vocabulary, on a schedule, instead of reading it once.