This idea sounds somewhat flawed to me based on the large amount of evidence that LLMs need huge amounts of data to properly converge during their training.

There is just not enough available material from previous decades to trust that the LLM will learn to relatively the same degree.

Think about it this way, a human in the early 1900s and today are pretty much the same but just in different environments with different information.

An LLM trained on 1/1000 the amount of data is just at a fundamentally different stage of convergence.