People will keep hiding reasoning because it allows prompt injection https://arxiv.org/pdf/2603.12277, in addition to facilitating distillation (you don't pay the full cost of RL)
https://developers.openai.com/cookbook/examples/responses_ap...
Gemini (the web UI) used to show raw reasoning, or at least a more detailed summary of its reasoning, less than a year ago. Complete with markdown and weird spelling idiosyncracies, so I'd lead towards "real reasoning", but who knows. The reasoning block leaked the system prompt way more often than the response block did, and you could figure out why it would refuse a request through the reasoning, even if the response itself refused to elaborate. This is, presumably, why they stopped showing it. No loss for them, just prevents "pesky users" from low hanging fruit snooping.
(Gemma 4's reasoning and output remind me strongly of what I remember Gemini 2.5/3's reasoning to be, as an aside. I guess that's obvious, but Gemma 3 felt like a totally different model, while 4 feels very Gemini-ish.)
That said, including instances of the attack in training is already a good countermeasure.
For example, gpt-oss loves reasoning in the style of "I be caveman, hungry, need food, need coconut, will search coconut now, eat when find." Giving that to a model unaccustomed to that style could cause it to respond like that.
Reasoning interpretability helps debug why models fail (and some labs will give it to you if they trust you not to distill or be hacked), but there are also conflicting goals like token-efficiency, so interpretable reasoning doesn't always mean "pretty sentences".