What counts as a population in general theories of evolution?

I stumbled across a paper today (by Karim Baraghith) on a topic near to my heart. It addresses the question of: what counts as a population in forms of "generalized Darwinism".

It gives what seems to me to be a very complicated answer. It says that a population should be defined using the: “causal interactionist population concept” (CIPC) - a concept it attributes to Roberta Millstein (2010).

Here is the paper under discussion: https://www.academia.edu/39977777/Investigating_Populations_in_Generalized_Darwinism

It introduces the causal interactionist population concept (CIPC) as follows:

According to Roberta Millstein’s CIPC (Millstein 2010, p. 67) emphasis added):
(a) Populations […] consist of at least two conspecific organisms that, over the course of a generation, are actually engaged in survival or reproductive inter-actions, or both.
(b) The boundaries of the population are the largest grouping for which the rates of interaction are much higher within the grouping than outside.

I think this paper is over-thinking things. I am strongly opposed to defining a population in terms that prohibit populations with one member. We do not need one theory for populations of size greater than two and another for populations of size less than two. That would be ridiculous! Evolutionary theory can and should deal with populations of any size. There is no rule that says their size must be two or greater. If there is only one remaining organism in a diminishing lineage, evolutionary theory should still apply. Nor is it the case that such populations do not evolve - or can only evolve to extinction. They can evolve via self-directed evolution, for example and they can also grow into larger populations. Size less than two is a basic requirement and must be supported! I think that we can put evolutionary theories that fail to meet this basic test into the trash basket.

Nor is it appropriate to reference concepts such as "organism", "generation", "survival" or "reproduction" in a definition of what counts as a population. In general theories of evolution, the simplest population concept is a set - a mathematical set.

There's no need for anything more complex than this. Or so I claim. In my support, I cite Occam's razor. If your theory or your concept is too complex, ditch it. This is a good case in point.