One of the benefits of using thinking tokens compared to “thinking in a latent” space is that you can directly observe the quality of the CoT. In R1 they saw it was mixing languages and fixed it with cold start data. It would be hard to SFT this because you can only SFT the final result not the latent space. I also notice the authors only had compute for a single full training run. It’s impressive they saw such good…
On a side note, there's decent research on how well bilingual humans do actually think in both language, and are actually better at decisive thinking outside of their mother tongue.