We have a full benchmark breakdown specifically on structured output that you can take a look at https://interfaze.ai/leaderboards/structured-output-benchmar...

> Smaller models really arent great at structured output.

That doesn't seem to hold true. Consider gpt-5.4-nano which supports structured output just fine.

https://developers.openai.com/api/docs/models/gpt-5.4-nano

It seems like a concern that's orthogonal to the model size.