I don't think there's anything in that article that suggests that the techniques only improved memorizing and not your specific definition of studying. Also, there are definitely things that I have learned and since forgotten that I had to think critically about and understand. I think this article is about techniques to improve the retention of knowledge.

Take, for example, the math students who had to apply formulas to find different properties of prisms. The students who learned and practiced all of the formulas at once (which most likely requires critical thinking to determine what each problem is asking for) did much better than the students who just practiced sets of problems for each formula sequentially (which is more like memorization).

I thought the most interesting part of the article wasn't the findings on varied environments or multiple shorter study sessions, but that studying multiple things in one session improved retention. Speculating as to why, the brain subconsciously makes connections between the different topics, strengthening each concept.