An advantage of the structured format is that you can intercept and stop showing the output to the user if the LLM starts generating a longer conversation. I've

An advantage of the structured format is that you can intercept and stop showing the output to the user if the LLM starts generating a longer conversation. I've had models go into a back and forth between the user and AI agent on their own, but at least it's easy to hide if it takes the structured format. It's harder than I expected to actually get an instruction tuned model to ask follow up questions, so it's interesting that it has to be explicitly asked no to. You may be right that they're going for some side effect.