Flipping back to the second sheet, you notice the various designs are built around certain joint configurations. Twilight must have been working out which would be easiest for the spell to manipulate. At the bottom is a section separated from the rest, circled in red. Apparently the spell could handle position reporting itself, but also integrate whichever system you intended to use for that purpose. But it goes on to say there’s utility in making the spell work harder if it meant minimizing the number of independent channels for control and feedback the spell needed to track.