Larson does not actually SAY it, but it is inferred by the way he compounds motion--you either have to change aspect (space to time or time to space), change type (linear or angular speed) or change to another dimension. So it is more than just "reversals."
I am finding a number of these "unspoken rules" that he uses as I write simulations for RS2--I use AI-style "rule sets" to define behavior (microtheories), rather than just "code for results." If I can get them all defined, then reproducing Larson's work (or RS2) becomes extraordinarily simple--just follow the instructions, step-by-step!
Another one of the consequences of these implied rules is that motion always manifests as a duality, one aspect expressed as linear speed, the other as angular speed (the basis of the particle-wave concept). Normally, the "energy" component, t/s, is the angular speed for material structures. This is why a complex quantity works so well--linear + angular speed. This is also why you can move between the first unit (speed) and second unit (energy) of motion without any "energy" to flip it--you are not actually changing structure--same house, you just enter from the back door, rather than the front. You don't have to rotate the house in order to enter through the back door.
I know that there is also confusion regarding the fact that rotation is 1-dimensional, because people only think of rotation in an X-Y linear system, implying 2 dimensions. My attempt to fix that is to use the term "angular speed" rather than rotation, to try to get around something turning on a 2D linear plane, and go with the concept of "RPM" instead. Hopefully, that is coming across in a clearer fashion than Larson's "scalar rotation."
Right now, I am trying to address the "equivalent space" concept, the way time influences space and how it differs from "yin space" (the space region). It is a tough one, because the observed behavior is very similar, yet the distinction has to be clear in order to understand the cosmic sector.