Have you tried getting great, repeatable results out of an LLM? It requires great depth of knowledge - about both how LLMs work and the specific topic you are trying to build against - plus a methodical process in figuring out what works and what doesn't.

I see no reason not to label that "engineering".

I also think it's important to distinguish between prompting and prompt engineering. Prompting is when people type prompts in a box. Prompt engineering, by my own definition, is when developers build further software on top of LLMs.