4. Of course the adoption of a linear approach does not entail that development necessarily takes place in a smooth linear fashion. What it fundamentally relates to is the treatment of time where asymmetric connections between development variables are viewed in a linear sequential fashion. In other words the arrow of time is one-directional moving unambiguously forward in a positive manner.
In geometrical terms the line is one-dimensional (or one-directional). So in holistic mathematical terms linear understanding is likewise one directional (i.e. asymmetric).

The circular approach is symmetric in the sense that every (linear) asymmetric interpretation of development moving in one direction, has an equally valid opposite (mirror) interpretation that moves in the opposite direction. Thus the simultaneous balancing of both perspectives is symmetric in a dynamic sense.
Of course this entails that time itself in development is now treated in a relative bi-directional fashion i.e. as simultaneously moving in both positive and negative directions. The reconciliation of such paradoxical notions of time leads to nondual awareness of the continual present moment.
Again there are fascinating holistic parallels here with (analytic) mathematical notions.
In geometrical terms the circle includes its line diameter which moves bi-directionally in opposite directions from its centre point.
So in dynamic holistic mathematical terms, circular understanding includes bi-directional linear understanding emanating from a central spiritual point.
So pure spiritual intuition is necessary for appreciation of bi-directional understanding (which  in its developed form is directly associated with the "higher" spiritual stages of development).

There is also a fascinating psycho-mathematical connection here with the binary digits (1 and 0) with form relating to the holistic interpretation of 1 and formlessness (i.e. emptiness or nothingness) relating to the holistic interpretation of 0 respectively.
In the major Western religions there is a greater emphasis on form with a corresponding belief in One God (1).
By contrast in the more intuitive Eastern esoteric traditions there is a greater emphasis on formlessness where ultimate reality is seen - devoid of phenomena - as a creative void (0).
There are also intimate holistic connections as between the geometrical notions of the line and circle and the binary digits (1 and 0) respectively. 1 as a symbol is literally a straight line and 0 (with minor modifications) is in fact a circle.
Thus the dynamic translation of the relationship between form and emptiness at all stages of development entails the dynamic relationship of both linear and circular understanding respectively. This in turn entails the dynamic holistic interpretation of the binary system (1 and 0) i.e. where all transformation processes can be encoded by these two digits.

So Ken's own approach represents just one partial interpretation based on the understanding of the upper-middle level of the Spectrum.