Apep is a lesser hybridization of Chaos and Darkness.
The Egyptian personification of darkness itself is androgynous; the masculine Kuk and his feminine counterpart Kauket…who are much more ancient. They were viewed as one entity and yet simultaneously as husband and wife. This perception is extremely similar to that of Erebus and Nyx, though most tend to lean more towards their being separate entities rather than one. I, however, disagree…and view all of these entities as one in the same.
This further enforces your point though: many different cultures had different names for the same entity…the androgynous Darkness itself. Personally, I believe that Darkness leans more towards the feminine aspect of things and treat her as such…but I’m not going to get into my personal paradigm any more than that, as it would be a bit off topic.
I haven’t yet gotten the chance to delve into Koetting’s work, but I assume he’s not talking about Erebus himself…but the core behind all these varied perceptions: Darkness…probably the same vision that I’ve had throughout the course of my life. This makes me even more interested in his work because I’ve spent the majority of my life establishing the foundation of my spiritual views through an introverted process. It wasn’t until they were established that I began looking outward for similarities in the beliefs of others to enforce my own, I believe that this was the best possible path to ensure that I wasn’t tainted by outside perception.
Still, I can’t speculate until I get a chance to read his work…which I intend to do sometime within the near future.
Edit: I should also note that Kuk/Kauket is partially considered a deity of chaos, which I find to be inaccurate and unfortunate. This entity is the deification of primordial darkness, but anything of this nature is often simultaneously tied to chaos…be it birthed from such like Erebus and Nyx or simply associated by proxy like Kuk and Kauket. You often see the same type of blending when it comes to primordial forces of Light and Order, despite them being very different things. At least by my perception.