Also I suspect that, apart from that, the results on smaller, cleaner codebases are better. LLMs degrade when following more than N instructions (where N depends on the model) even if the context window is not full yet; I suspect they also degrade when code has too many unnecessary concepts and details
The idea is to use the LLM to analyse the code base first before taking any action.
I think I'm suggesting a centaur approach.
If they don't have good code to mimic, anything goes. They might use libraries or they might start to write their own implementation of a PNG encoder.