Certainly not just coding. Senior designers and copywriters get much better results as well. It is not surprising, if context is one of the most important aspects of a prompt, then someone with domain experience is going to be able to construct better context.

Similarly, it takes experience to spot when the LLM is going in the wrong direction it making mistakes.

I think for supercharging a junior, it should be used more like a pair programmer, not for code generation. It can help you quickly gain knowledge and troubleshoot. But relying on a juniors prompts and guidance to get good code gen is going to be suboptimal.

The funny part is that it completely fails in the area so many people are desperate for it to succeed: replacing engineers and letting non-technical people create complex systems. Look at any actually useful case for AI, or just through this thread, and it's always the same thing; expertise is critical to getting anything useful out of these things (in terms of direct code generation anyway).