I'm puzzled as to how that would work, when people talk about quick changes in model behavior. What exactly is being adjusted? The model has already been trained. I would think it's just randomness.
And fine tuning.
Choose your fighter...
High level overview: https://www.datacamp.com/tutorial/fine-tuning-large-language...
More detail: https://www.turing.com/resources/finetuning-large-language-m...
Nice charts: https://blogs.oracle.com/ai-and-datascience/post/finetuning-...
The big platforms also seem to employ an intermediate step where they rewrite your prompt. I've downloaded my ChatGPT data and found substantial changes from what I wrote. Usually for the better. Changes to the way it rewrites changes the results.