That's been going through my mind, too, and I totally agree. In any research, the terminology can be misleading, and I too am wondering if the term "struggle" is an accurate term to define all learning. In such cases as mentioned by a2z, I'm wondering if it's more similar to a correction rather than a struggle. Perhaps even more definitively, could all learning be defined as a paradigm shift. Perhaps a paradigm shifts in one of four ways: changing what the student thought s/he knew, confirming what the student already knew, adding to what the student already knew, or providing the student with totally new information. In all three cases, though, the new information is connected with previously learned knowledge. I am still seeing a strong benefit in challenging all students in the classroom.