I guess Theistic evolutionists do separate the material and spiritual worlds ignoring the influence of the latter. But they are not Gnostics in the strictest sense lacking faith in Demi Urges and a horror of the physical world as somehow spoiled. Also, their reflections are based on a celebration of and fascination with the physical world over a literal interpretation of what God has said. Theistic Evolutionists are more Deistic with occasional Divine interventions in some versions.
Not Gnostics 'in the strictest sense', but by that logic not Christians either, because all the Christians of the first few centuries AD were creationists as well. What seems to have happened is that both Gnostic and Christian thinkers followed the same philosophical threads to shuttle God to a realm strictly outside of nature. Gnostics no longer required a Demiurge character, because nature itself became the demiurge of ignorance, acted out in a primitive world before gnosis occurred in the minds of men.
The central gnostic element is the view of humanity and world history as being within a state of a transformative "becoming"... a belief in the universe unfolding in a rational way, according to human reason. Humans are conceptualized as the substance of the universe becoming aware of itself. This is the core spiritual thrust of the humanistic modern period, 16th-19th centuries.
Modern science is based on this philosophical revolution in the minds of men. Modern science is not merely a method but a philosophical shift from the recognition of an order of being outside of or above nature, to a system of knowledge about the universe based only on how man could conceive of it in a rational way. Approaching reality in a strictly empirical and rational way means you are going to interpret the history of the universe as a dialectic materialistic process... or the continual "becoming" of a transforming nature.
This type of 'science' is the essence of gnosticism, and it's where we get our one-dimensional evolutionary interpretation of reality. A gnostic thinker views enlightenment as a progressive transformation from darkness and ignorance to a state of illuminated reason... he dispels the tricks and illusions of nature with the powers of reasoning in order to transcend the state of nature (stardust becomes aware of itself) ... and so this same idea of rational progress is projected onto the nature of reality itself, and the end result is the belief that everything must have evolved.
God is not supposed to be found interacting in the state of nature, (e.g. traveling around the middle-eastern wilderness in a pillar of cloud) because gnosticism identified the true god with his rational awakening to reality itself. The idea of scientific enlightenment is considered to be that rational awakening to the true reality behind our illusions about the earth being 'poofed into existence' by God.
So in the theistic evolutionist's worldview, world history is this same type of process of human development from primitive material roots up to the acquisition of scientific enlightenment, when humanity dispels ancient ignorance and acquires a divine gnosis into the true nature of reality.
This is also the basic philosophical Enlightenment narrative of "science" being a new system of actual knowledge that reveals special truth about reality that was previously hidden. "science" here is a code word for Gnosis. It is not simply a methodology, but a real belief that the fundamental nature of reality has been unveiled through the illumination of man.
But this belief is itself based on a kind of circular argument that the rational and naturalistic interpretation of the universe must be the most correct one. This is the assumption that is not to be questioned, and we are simply told that explanations which only include 'natural causes' are axiomatically the best ones. Modern science is based on a philosophical system that strips the idea of an immanent God out of reality and forbids the questioning of it.
That is why people believed in evolution long before there was any real scientific theories for evolution. The belief in evolution was a consequence of the humanistic gnostic philosophy of a progressive human nature, ascending towards enlightenment. The scientific theories that came along later were just attempts to figure out how everything evolved rationalistically, but these theories were all based on a mode of thinking that was incapable of questioning whether or not a rationalistic evolutionary process actually occurred.
Long before Darwinism, the conclusion of Evolution was already baked into the cake. And today everyone is very familiar with that feeling that one is not allowed to "question the science"... It's that essential forbidden-ness that usually accompanies a religion.