While there may be more going on, this explanation certainly makes sense. It intersects with what modern research (and human wisdom going back many years) demonstrate, namely that memory itself is shifting and malleable and, indeed, creative. This understanding of memory is, I believe, now widely held -- but if memory is like this, isn't recall (to use a different term to describe the particular form of memory involved in the process of study) probably also like this? If recall and memory in general are similar, then recall in study is not, at least not necessarily, a process of rote repetition or regurgitation.
Moreover, recall would be more than just a change in our access to information, of the sort Professor Bjork discusses. Recall would be an ongoing process of fitting the information in question with other information we already have or subsequently acquire. Recall, then, is a form of working with information -- and efforts to replace students' practice of recall with processes of working with ideas (such as concept mapping, one of the alternatives examined in these experiments) miss the point that recall itself is working with ideas.
There may be memory chores that have no other mental significance, though I'm not sure we can assume this without actually examining what those chores' impact on the mind may be. But even if there are drills so unenlightening as to be "mindless," the import of these experiments seems to be that tests that demand the exercise of memory can be quite deeply mindful.