> I wonder if open models are going to start doing that too

Yes, some of them do do that. For example Moonshot tried to reward shorter reasoning traces in between Kimi-K2.6 and Kimi-K2.7 Code, and the latter has a mild caveman accent in its reasoning traces that the former lacks.

Qwen3.8-Max also has terse reasoning, but I don't remember this being the case for Qwen3.6 models I ran locally.