I suspect that the composer, Michael Kravchuk, did not intend these exercises to be seen as the One and Only Solution to Learning Sightreading. You're just supposed to include a few of them every day as part of your overall sight-reading training material.
Instantly transposing them into any key (thanks to MusicXML) at least gets you all over the keyboard, in seconds. As for limited position, you can pretend that each new exercise starts at a different tetrachord, if you like. Whatever. It's just a little extra new material. There is no such thing as a SINGLE EXERCISE that can teach all of sight-reading. The point is to see the widest variety of material, no single example of which can possibly include all aspects of possible reading.
By the way, I tried converting the entire book into MusicXML, but the result was riddled with errors. What I ended up with is of some personal use perhaps, but certainly not fit for sharing. Music scanning and MusicXML and all that stuff is technology which is still in its infancy, and it's shaping up to be a LOOOOOONG infancy. Clearly the technical challenges of digitizing music notation are not yet within human capacity to fully master.