The LLM does not have the ability to tell you what it knows and what it doesn't know about a subject. In order to get information out of it, you need to present it with a pattern that matches with something it was trained on.
An example, is that an LLM can tell you how many programming languages it knows, how much it knows about them (which one it understands best), and how many it doesn't know. If you ask it a question like "how to do X in python", it will have been trained on something that roughly matches that and give a response, but if you ask "what things do you know how to do in python", and it simply is not capable of giving a response.
I'm not sure that this means it doesn't have some form of understanding of things, and I do believe that AGI is possible to create in general with sufficient technology, and I do realize that our brains may work in a similar way, but I think LLMs are missing something when it comes to understanding and creating that we have not yet figured out.