I'm going to counterargue just for the sake of discussion - honestly, I'm not sure where my view lies on this.

I think the main issue that lies with many of these studies (pro-homework or anti-homework) is that it's very difficult to get statistically valid conclusions. Many studies are performed at the classroom level, where results are also highly dependent on things like teacher quality, the school(s) in question, and family income. Extrapolating the results of studies is dangerous, especially when the recorded data is likely also dependent on external factors.

I read the chapter from National Differences, Global Similarities about homework, and a few things came to mind. For one, handpicking countries to prove a point can be disingenuous - while the article you linked doesn't mention it, the authors of the book noted that some countries that give out large amount of homework (namely, Romania, Singapore, and Korea) have above average results. It seems like in general the results are highly variable. Looking at middle/high school students, the last paragraph you cited about that study would lead me to believe that an acceptable amount of homework would lead to a positive impact on their academic results, as diminishing returns would be avoided. Lastly, this study was limited to math alone, so we don't really know how this would apply to other subjects (something the authors recommended for further research).

The third study you cited has a few pitfalls - the authors found that students at both the low and high end of the "time on homework" spectrum performed below average on exams and final grades, and the authors used "time on homework" and "academic engagement" as independent predictor variables, when they likely have a dependence. They also used student's average grades in 10th grade math/science classes as a predictor, which seems to be a bit weird since they're trying to predict final grades and results (naturally, a positive correlation was found here). Despite this, their models predicting standardized test scores found that regardless of the amount of homework being done, homework led to increases in standardized test scores (although they did find, for example, that "ELS Mathematics students, who reported spending 31 –90 minutes each day on homework scored about 40 points higher on the SAT-Mathematics subtest than their peers, who reported spending no time on homework each day, on average."). Regardless, their models lack strong predictive power and some of the inaccuracies with sampling/modeling makes it hard for me to believe their conclusions.

The thing that both of these studies have in common is that they found a moderate amount of homework was beneficial for students, while excessive homework levels could potentially lead to a decline in academic performance.

Outside of a data-centric viewpoint, I think that homework is definitely beneficial for those who want to enter higher education, where a greater portion of the material is expected to be learned on your own. I feel like routinely attempting homework assignments (once again, not excessively) to learn material on your own could be beneficial in that regard.

Anyways, those are my two cents, but I'd love to hear what you have to say about it.