In this case, by "arbitrary" I meant anything we would ask of it. But I don't understand why a machine that is able to reliably write code would be unable to reliably design software. Currenly, LLMs do neither, but if we're imagining what they could do some day, I don't know why we'd think it could do one but not the other. And a machine that can reliably write code can also probably reliably run a company as well as if not better than a human CEO.

Fair enough! I would wager that shaping what we ask of it will become more important, remain non-trivial, and good software will integrate software design and company design beyond what it is today. Someone or something has to bring a vision and a reason why the thing is being done at all. I imagine as long as taste exists, that will involve humans at some level.