Currently, whenever a LLM produces a result that looks like deeper reasoning, it's easy to explain that with "eh, there was probably something similar in the trainset that the LLM just had to tweak slightly" - and that argument is basically impossible to refute or confirm, because the trainsets are huge, chaotic and often only partially available (Books2...). Therefore we can't really make any good statements about what information could or could not be pulled from the trainset.
I think it would be interesting to pretrain an LLM on a selective corpus - say, the entirety of Discworld or A Song of Ice and Fire novels - and then observe if the model can produce output that is not obviously stitched together from the books.