Right: software is not necessarily a sufficiently-clear specification, but a sufficiently-clear specification would be software – and you've correctly identified that a good part of your job is ensuring the software provides a sufficiently-clear specification.

Amazingly-written software is necessary for LLMs to work well, but it isn't sufficient: LLMs tend to make nonsensical changes that, while technically implementing what they're asked to do (much of the time), reduce the quality of the software. As this repeats, the LLMs become less and less able to modify the program. This is because they can't program: they can translate, plagiarise, and interpolate, but they're missing several key programming skills, and probably cannot learn them.