Humans would say "Left" 100% of the time in a zero-shot scenario as well.
Intuitively, your first response is going to be "left" since it has the 80% probability. You'd balance your answers over time when you realized you were closer to 90% by some arbitrary internal measurement (or maybe as you approached 10 iterations).
I'd expect an LLM to generate an approximation similar to a human - over time. Turns out Humans can't do probability either. If you test the LLM multiple times, similar to how you'd ask a human multiple times, they tend to self-correct.
Whether that self-correction (similar to a human) is based on some internal self-approximation of 80% is for someone else to research.
Example session: Prompt: "....probability prompt" LLM: "left" Prompt: "again" LLM: "left" Prompt: "again" LLM: "left" Prompt: "again" LLM: "right" Prompt: "again"
This was my session with GPT-4.