This can actually be true, depending on how the system is configured.

For instance, if you and someone else use the same locally-hosted Stable Diffusion UI, both put the exact same prompt, and are using the same seed, # of steps, and dimensions, you’ll get an identical result.

The only reason outputs are different between prompts is because of the noise from the seed, normally randomly set between generations, which can be easily set to the same value as someone else’s generation, and will yield an identical result unless the prompt is changed.