Barry Garelick, via a kind email:

An important part of the job of teaching math in K-12 is to stretch students–to teach them creative and personal engagement with the material. At some point this must involve expecting students to come up with previously unfamiliar steps on their own for new problems that do not lend themselves to known algorithms, prescribed methods, and predictable approaches. An effective way of doing this is to extend routine problems that students know how to solve into nonroutine problems.
Over the past two decades, however, disagreements between advocates of traditional or conventional math teaching and the math reform movement have resulted in a fragmented approach to teaching math. A key area of disagreement centers on the distinction between “exercises” and “problems”. Math reformers generally believe that conventional math teaching consists mainly of routine problems that are nonthinking, repetitive, tedious and do not lead to students learning to solve nonroutine problems.