The unpredictable part isn't new - from a project manager's point of view, what's the difference between an LLM and a team of software engineers? Both, from that POV, are a black box. The "how" is not important to them, the details aren't important. What's important is that what they want is made a reality, and that customers can press on a button to add a product to their shopping cart (for example).

LLMs mean software developers let go of some control of how something is built, which makes one feel uneasy because a lot of the appeal of software development is control and predictability. But this is the same process that people go through as they go from coder to lead developer or architect or project manager - letting go of control. Some thrive in their new position, having a higher overview of the job, while some really can't handle it.