[jsenn]

This is discussed in the "Watermarking with Synth-ID Text" section right after they define the Score function:

> There are two primary factors that affect the detection performance of the scoring function. The first is the length of the text x: longer texts contain more watermarking evidence, and so we have more statistical certainty when making a decision. The second is the amount of entropy in the LLM distribution when it generates the watermarked text x. For example, if the LLM distribution is very low entropy, meaning it almost always returns the exact same response to the given prompt, then Tournament sampling cannot choose tokens that score more highly under the g functions. In short, like other generative watermarks, Tournament sampling performs better when there is more entropy in the LLM distribution, and is less effective when there is less entropy.