Bostonian, I wonder if that supports
strand-based pedagogy-- or if it is more of an affirmation of adaptive/mastery-based pacing. Clearly the latter is a good thing because it automatically keeps students in their proximal zones and learning well.
I will say that I had to laugh a little when I read:
Some advantages of strands could be that
(1) changing topics after a few minutes maintains interest
(2) if a student is stuck on a topic, he can still move to other strands and feel successful
I laughed because the former is the precise thing that drives my own top-down, mastery learner to distraction about the way that math (or anything else) is commonly taught in schools. She calls this the "ADD model of education."