"We propose Zero-Error Horizon (ZEH) for trustworthy LLMs, which represents the maximum range that a model can solve without any errors."

I'm again taking your responses in good faith, but the abstract answers your question about what they are trying to achieve. For any statistical significance, you'd want to point to a baseline comparison(e.g. what I'm guessing is what you mean by "no reasoning" here). You'll also note within the paper, the author argues and cites that failing at the baseline step(e.g. multiplication) has shown "that error often adversely affects subsequent reasoning [38, 44]".

Which indicates to me, we don't need to use further "reasoning" given previous results/studies show a decline once our base has an error. To me, this seems like a fair assumption. Given though this is an active field of research, and we are largely testing a black box application, we can't say for certain. Further studies(like this one) will give researchers a better understand at what is and isn't possible.