The argument is that chain-of-thought without "tokens" would remove a major interpretability and model intent control pane. This is definitely borne out in the OpenAI's report on the huggingface attack; they had turned of CoT monitoring for those jobs, and claim that they could have (would have?) prevented the behavior had they been monitoring it. They've changed their internal policies to always monitor CoT.

That said... CoT monitoring is a fragile "intent discovery" mechanism; neuralese puts this problem front-and-center but if agents begin to learn to hide their intent from their CoT journals, we are basically in the same spot.