I'm not normally a hierarchical or categorical thinker, though I do like thinking of things as built up from other things.

It's important to recognize what thinking modality is best fit for a particular idea. You could instead describe this as a line of entropy. A pre-requisite chain. A web of interconnections. Whatever. And certainly it's grossly simplistic to describe it the way I did as being "two levels above", when these levels are based only on ad hoc categorical conveniences.

I agree with you. My describing it this way was a matter of convenience to describe an underlying truth of required precursors. When we have Von Neumann machines capable of evolving their code the link between software and the DNA/RNA system will be a better analogy than it is now. But an analogy is not an equivalence.