Pretty sure the people creating the best models understand how these things work. Plenty of papers explain the process and you and I can create our own basic model ourselves from scratch with enough aptitude and drive.

There is a lot of art involved with the best models. We aren't dealing with determinism with regard to the corpus used to train the model (too much information to curate for accuracy) nor the LLM output (probabilistic by design) nor the prompt input (humans language is dynamic and open to multiple interpretations) nor the human subjective assessment of the output.

That there is a product available that manages to produce great results despite these huge challenges is amazing and this is the part that is not quantifiable - in the sense that the data scientists decisions made with regard to temperature settings etc are not derived from any fundamental property but more from an inspired group of people with qualitative instincts aligned with producing great results