I like a great deal that one of the considerations the authors make is adapting to prior knowledge. (3.1) describes what they looked for in detail. In their summary, "None provide personalization based on prior coding experience or learner goals, other than rudimentary age-based differentiation." Its hard to overstate the importance of prior knowledge. Prior knowledge has some of the highest effect sizes in educational research. In other words, what you already know going into it is going to determine how much you learn. It's rare for other factors to have the same impact on the results as prior knowledge. And yet, even given decades of learning science research, its pretty rare to see much of any attempt in Western learning to account for prior knowledge. It would be a refreshing change of pace to see some of these coding tutorials work in preemptive assessment to figure out where to focus the learner before getting into the "how" of it.

Disclaimer: I'm working on sagefy.org