The most naive guess is that they may be using some special type of CoT that is more effective at delivering the right answer than what you’d get by default. If their competitors saw it, they would try to replicate it (not even train on the CoT, just use it to guide their design of the CoT training procedure).
Why doesn’t Open AI allow people to see the CoT? This is not good for their business for obvious reasons.
The most naive guess is that they may be using some special type of CoT that is more effective at delivering the right answer than what you’d get by default. If their competitors saw it, they would try to replicate it (not even train on the CoT, just use it to guide their design of the CoT training procedure).