What you are saying is true to a degree and debugging was 90% of the work in my career. Finding the smoking gun IS the key as you said.
It depends on where the developer is at in their journey too.
For some, "look in the logs" is a challenge just to find out what they are and where to find them and what they are saying. A great piece of advice for a person in this position.
For others, "There are files that hide in the caves of your computer's consciousness. Find what causes the shadows on the walls." is a valid call to dig deeper :)
It might seem obvious to look at the logs, but in my experience 90% of being stuck debugging something is just not yet having looked at all the available evidence.
It's true you could learn these habits by exposure to them, and this could be a neat alternative to pairing with a more senior engineer for that. But it looks like you could easily just keep saying "it's random", "I don't know", and the model would keep telling you what to do next, without you actually having to think.
I wonder if making it even more Socratic would fix this? E.g. "how do you know it's returning 403s? Oh, logs you say? Is there anything else they could tell you?"