• “Most useful when we're studying” and “Most useful when we're working” are clearer (and also more precise!) than abstract (“chunking”) terms like “Acquisition” and “Application”.
• Similarly, “Practical steps” and “Theoretical knowledge” are clearer than “Action” and “Cognition”.
• For that matter, the “-oriented” suffix in “Learning-oriented”, “Problem-oriented”, “Understanding-oriented”, “Information-oriented” is helpful, compared to the “Learning”, “Goals”, “Understanding”, “Information” abstract nouns.
What is common to all three sets of differences is that the former labels (on the older diagram) actually carry with them their semantic category (what kind of difference is being described, namely: (1) when useful, (2) what contents, (3) what's the orientation), while in the newer diagram everything is just abstract nouns. (E.g. “Useful during application” and “Useful during acquisition” would still be an improvement over just “Application” and “Acquisition”, though the older labels are even more direct and clear, without requiring the reader to engage in psychology to think abstractly about terms like acquisition.)
Also (separate complaint), whenever I want to tell anyone else about this "four kinds of documentation" approach, I always link to the archived https://web.archive.org/web/20200312220117/https://www.divio... which is the latest version that is entirely on a single page. Both the current version on the Divio site and on the Diataxis site seem “overdone”; a prospective reader has to click on “next” several times and it's unlikely they're going to do that.