I dislike both options, since "learn" and "knowledge" are overstating things, but of the two: Preloaded.
That first metaphorical human child would be suffering from devastating anterograde amnesia and would periodically be eliminated and replaced with a fresh clone from the Training Vats.
I say "overstating" because a lot of what we humans perceive from LLMs is a kind of self-trickery. Other humans are using the LLM to generate a document that contains fictional characters interacting, and then "acting out" one of the character to make us confuse the character with the author, and then human intelligence and knowledge is (automatically, instinctively) engaged in "filling in" the character being described.