Earlier quoted context omitted.
The primary source is: measured LLM performance on once-human-exclusive tasks - such as high end natural language processing or commonsense reasoning. Those things were once thought to require a human mind - clearly, not anymore. Human commonsense knowledge can be both captured and applied by a learning algorithm trained on nothing but a boatload of text. But another important source is: loads and loads of mech inter…
I haven't seen LLMs perform common sense reasoning. Feel free to share some links. Your post reads like anthropomorphized nonsense.
TL;DR: Even without being explicitly prompted to, a pretty weak LLM "realized" that a thousand glasses of water was an unreasonable order. I'd say that's good enough to call "common sense".
You can try it out yourself! Just pick any AI chatbot, make up situations with varying levels of absurdity, maybe in a roleplay setting (e.g. "You are a fast food restaurant cashier. I am a customer. My order is..."), and test how it responds.