alt Hacker NewsIt's exactly how it works - at least potentially. Lean text is harder to watermark because word choices and meanings are tightly constrained.
Low-entropy text is fluff and filler. It's very easy to synonym-substitute words without changing the message - if there even is one.
You're assuming they're training the model to maximize the watermark signal, on top of already adding the watermark. I suspect that would hurt model performance quite a lot, and simply be unnecessary... the watermark tech works well enough as it is.
As far as I know, anthropic aren't intrinsically motivated by watermarking (if anything it hurts sales, and seems indifferent to safety(?)) they're simply doing it to fulfill the EU obligations.