Good catch. Yeah, I think their hell is somewhat leveled like Dante's Inferno and a barren landscape, not a true "Void / Oblivion" as the bugs see it.
Again I've seen parallels though in teh Kilrathi and Kzinti as to a special fear of death in space. Its as though if they die dishonored on a ship, or a planet, then at least they have that much in the afterlife (wrecked hull, barren landscape, hardly makes a difference. At least it still has "something" there. A wrecked ship like a carrier or destroyer has enough mass that the bulk of the superstructure will hang around. There's a memory of air, a memory of sounds and smells. There's a "deathly remnants" or "reminder of what life was". A concept of there being enough external reference that the self-spirit can maintain itself on memory.
However, that being said...
If they die as a fighter pilot in space, their fighter pretty much gets blown to bits and the very low mass gets scattered very quickly by solar winds, other fighters, etc. They truely get "trapped in the black hell" because they don't even have a wrecked ship to sit on. The caress of a "true void" becomes much more real, much more frightening, because you loose any external self-reference points.
Alternately explained why this is a terrifying death:
I don't know of the human term for it, but the phoenix term I've learned is "using internal memory like a battery". If you have external remnants you have external reference points, thus you draw on your own internal memories more slowly because your mind is more distracted from doubting its own existance. Without the external reference points to distract you, your mind-spirit "drains the battery" more quickly.
The scary thing is, the chart runs on a curve much like the E=mc^2 formula, except the "E" is your existance and the "m" is the mass of memories.
When that battery runs out, well, you start becoming less of a "self-entity with importance and concept of self" and more of a "tiny insignificant part of a larger thing, unable to determine importance with an ever increasing doubt that are real or at least once were real." Which means that your spirit/soul/whatever has ever increasing difficulty identifying itself as a seperate entity from the rest of reality/existance. You loose the ability to process information at any level... sentient thought (as any living thing would recognize it) would become increasingly random and intermittant.