I can’t read the full article because it’s behind a pay wall, but from reading the abstract, I’m going to respectfully disagree. I don’t think this study is supporting your claim. This study is evidence spaced repitition works, in that reviewing old material with new material is more likely to retain memory than if you were to bunch all the reviews from a single lesson at once.
Experiment 1, college students learned to solve one kind of problem, and subsequent practice problems were either massed in a single session (as in the standard format) or spaced across multiple sessions (as in the shuffled format).
The way Wanikani works isn’t analogous to a Math textbook. In the standard math textbook this study is critiquing, you would learn something in lesson 1, review it all at once at the end of lesson 1 in the form of X number of questions, and then never return to those reviews as you progress through the book. From what I can gather, they’re arguing if there are 10 questions at the end of Lesson 1, the student should study 1-2 of them, and then the other 8 will appear at the end of other lessons. While not exactly spaced repetition, this works for similar reasons. Over time as they progress through the book, they review old material. They’re not cramming, they’re spacing their reviews.
Wanikani doesn’t present you all of Lesson 10’s items and force you to review them once and only once. By design you’re reviewing them over time, as the reviews become available again. It’s just not analogous to this study at all. Similarly, reviewing the meaning and reading at the same time isn’t the same as “bunching” your reviews, because you’re still reviewing the context multiple times over time, exactly what this study is arguing for.
In Experiment 2, students first learned to solve multiple types of problems, and practice problems were either blocked by type (as in the standard format) or randomly mixed (as in the shuffled format).
This experiment might support your claim, but I don’t know what they mean by “types of problems” and so I really have no idea what the equivalent would be in Wanikani. Does this experiment imply a type of problem is subtraction, and that grouping a bunch of subtraction problems together is detrimental? In the case of Wanikani is “reading” in general a type of problem? Or is the reading of a particular word a “type of problem”. If it’s the former, even if you’re reviewing meaning and reading of a word back to back, you’re still shuffling both those “types” of problems over the course of a full wanikani review. You’re not just doing reading over and over, and then moving on to meaning. If it’s the latter, a math problem is structured completely differently than recalling vocab of a particular word. I just can’t see how you could try and get this granular with this particular study and try to apply it to learning a language without actually conducting the study with language learning. Many other SRS systems provide reading and meaning back to back and yet people overwhelmingly report success using something like Anki.
To your other point, I hope I didn’t imply that the developers of WaniKani haven’t thought through their system. But I also don’t think WaniKani is a perfect system. There’s no such thing. For example, Wanikani uses spaced repetition, but on reviews, doesn’t present you with the review that is most important to review first, it just gives you them in a random order. Here’s a user script that attempts to fix this: WaniKani SRS Reorder Button. There’s plenty of evidence that timing matters in SRS. If you learned something 3 hours ago, and something 6 months ago, it’s more important you review the one from 3 hours ago sooner, because you’re approaching the time when your brain is most likely to forget it. A mature review can wait another day and the difference in recall will be negligible. The reality is everyone is limited in their time. Maybe you have 200 reviews and only have time for 100 of them. In that case it’s in your best interest to prioritize accordingly.
All this being said, I use (and LOVE) WaniKani because it offers a structured way to learn kanji and vocab, and provides built in reviews in the form of spaced repetition, which is one of the most effective ways to commit something to memory. In other words, it’s an amazing, incredible tool in my language learning repertoire. To my original point, just because I might think forcing yourself to agonize over perfecting learning specific words is a waste of time doesn’t mean I think WaniKani itself is a waste of time. Leeches are a common concept in SRS. Many other SRS systems will just bury a leech item for this exact reason, because it’s not a good use of your time to force yourself to memorize something using flashcards if you’re spending too much time on it. More likely than not, if you eventually need to learn a word, you will do so in another context. This is not an argument against WaniKani by any means, and offering critique of it doesn’t imply it’s not a good resource.
In the grand scheme of things, if your goal is to learn a language, and because of the design of a particular system, that person is discouraged and eventually drops off learning, then this is all for nothing. That’s what I was trying address in my reply to the OP. Literally none of this matters if they don’t continue their learning journey. And if modifying WaniKani so that you choose to do your meaning and reading reviews back to back enables you to learn more and experience more of WaniKani, and in turn learn more Japanese, then that’s a no brainer to me. People get hung up on perfection and optimization. None of that matters if you give up in 3 months.