Very interesting. I haven't read the paper in detail, nor have I seen the M&I textbook (but I've heard of it). But I've read several excellent
pedagogical papers by R. Chabay and B. Sherwood, the authors of that textbook (as Andy points out), over the years. (A couple of Sherwood's earlier papers straightened me out on a few topics that I didn't even know I was messing up.