The moment you start building evaluation pipelines and running experiments to validate your ideas it stops being guessing
Engineering: "Will the bridge hold? Yes, here's the analysis, backed by solid science."
Pseudo-engineering: "Will the bridge hold? Probably. I'm not really sure; although I have validated the output of my Rube Goldberg machine, which is supposedly an expert in bridges, and it indicates the bridge will be fine. So we'll go with that."
"prompt engineer" or "context engineer" to me sounds a lot closer to "paranormal investigator" than anything else. Even "software engineer" seems like proper engineering in comparison.
Right now, you cannot get that far. And if you happen to... Tomorrow it will be different.
Predicting tides is possible. It requires enormous amounts of data and processing to be sure of it. Right now, we've got tides, but we don't have the data from the satellites. Because the owner is constantly shifting the prompt, for good reasons of their own. So we can't be confident - or we can only be so blindly.