A couple, named the Arno's, licensed the system, but mapped the four temperaments to it (and discovered "extra space" so to speak, that did not fit in the ancient four, and so became a fifth). Temperament, of course, is apart of an inborn typology.
In my studies; I've determined that Inclusion corresponds to Interaction Styles (E/I + NP/SF; NJ/ST), and Control is Keirsey's groups. (S + J/P; N + T/F).
I forget if Schutz or Ryan ever used the terms introvert and extrovert. They might not, since they didn't believe this is really apart of the person. But yes, it is their grid that implies those terms as well as ambiversion, when extended to inborn temperament.
Since this system is based on a 2D 10x10 grid, scores of 4 or 5 in either dimension are considered moderate. Since low expressed Inclusion (eI) scores correspond to "introverted" temperaments (such as Melancholy), and high eI scores correspond to extroverted temperaments (Sanguine, Choleric), then eI of 4 and 5 is technically ambiverted. In MBTI, they will still have to be either E or I, but they may have difficulty determining which.