My read of what is being suggested is that the level at which one should aim to understand and be comfortable with is slightly more abstract than reading the code and reviewing every line of it. It is like how one is comfortable not understanding the byte-level code or assembly language code. I know that this analogy doesn’t hold very well because compilation is a deterministic process while llms are not, but that is precisely the point being made. “Trust” that llm will produce the right output, even though the output might not be reproducible word for word the next time you give the same prompt.

To your point about becoming redundant without understanding, not understanding things will be a problem when an issue arises and the other person isnt able to handle it the right way. However, if llm can address the issue, does the fact that they did not understand the details really matter? From the perspective of a person who gets to decide who gets fired, would they fire someone who is productive but sometimes introduces bugs that they quickly address or would they fire someone who is comparatively slow but rarely introduces bugs? The answer probably depends on the domain, and how costly a bug can be. For most of us, the work is not so critical that you cannot afford bugs. So, productivity wins.