Starting from a platonic perspective of strict form the vortex begins with a 0d point and ends with a 0d point...it is circular in nature as the end point is the same as the premise. This is from a standard geometric perspective.
In non scientific symbolism, ie religious (Hinduism, Paganism, etc), the vortex is viewed as both a creative and destructive force. A creative it results in the formation of form through a self negation. Void is voided.
This double negation is observed within the groundings of intuitionist logic. It is also observed in the simple axiom of a line (segment) between two points in Euclidian geometry where the point negates itself (formless negating itself) into a line (form).
The new form in turn is negated into a new form, as void is not subject to time or space...and the process spirals.
The spiral is thus a perpetual curve between two points, as observed by the golden ratio...and as such is circular. This is considering the beginning and end point of a line or spiral are both a 0d point or "void" in more abstract terms.
This force is a universal platonic form.
Jung, in his formulation of the word "archetype" observed these platonic forms under the context of psychology and observed its creative potential.
Eastern Philosophy observes Kundalini energy as a spiral as well.
We see these vortex forms replicate in a myriad of ways within nature ranging from tornadoes to hurricanes to sea shells.
These natural phenomena show a destructive nature (storms wiping out buildings, sea shell ending the assault from a predator) and creative (storms creating new clear space as well as watering potential vegetation, sea shell protecting life).
It is observed with the golden ratio of math, as well as the progressive cycling of 1 through the number line.
It is observed in the rotary movements of sports, as well as the cycles that consist of the human body.
It occurs within the nature of tautology, as observed by Wittgenstien as well as the progressive spiraling of definition we see whenever we loop up any word within a dictionary.
This can be observed simply in aristotelian identity properties:
In observing the identity of P a cycle occurs, as something cannot equal itself unless it is self referencing. This identity is thus a context of self-referentiality.
Thus one context leads to another context as a variation of the original.
This is a tautauolgy and recursive.
One context breaks down into another with a new context being created.
The examples are boundless.
However, considering Neitzche's premise of everything being a contradiction we are left to pointing towards the fallacies. The simplest of these fallacies being the Trillemas of Munchausseen, Agrippa and Frie.
They observe directly or implicitly:
- All is assumed points of observation.
- All is regressive definition.
- All is circular.
We are left with a spiral form in understand the core foundations of what composes the fallacy.
Thus Neitzches work, intentionally or not, is premised on these fallacies and his perspectivism is grounded in them. This is reflected further in his pessimism of society spirally to destruction as well as the modernist, as you claim, interest in the spiral.
The modernist view, premised on industry being the foundation of modernism, is grounded in the spiral use of resources where we use resources to create technology that uses more resources in order to create more technology to acquire more resources.
These resources can be from anything physical, to simply being the harvesting of humans attention through consumerist entertainment industry (we spend resources on entertainment in order to promulgate more resources on entertainment...etc.)
Thus to address your two sentences.
The eternal return is natural as evidence by the forms in nature.
To will the eternal return is to force the internal return, but to force what is already occurring is to break it.
But is cannot be broken as we end up using spirals (see argument above with industry and logic) to do it.
Thus we create many forms out of one causing the return to become more complex.