The analogy to assembly is wrong. Even in a high level language, you can read the code and reason about what it does.

What's the equivalent for an LLM? The string of prompts that non-deterministically generates code?

Also, if LLM output is analogous to assembly, then why is that what we're checking in to our source control?

LLMs don't seem to solve any of the problems I had before LLMs existed. I never worried about being able to generate a bunch of code quickly. The problem that needs to be solved is how to better write code that can be understood, and easily modified, with a high degree of confidence that it's correct, performs well, etc. Using LLMs for programming seems to do the opposite.