Because at the beginning I didn't trust it and verified it in many different ways. I've got a fairly decent understanding of what LLMs hallucinate regarding language learning and levels, and luckily/unluckily I'm far enough for this to be a concern. e.g. I asked recently differences between 回答 vs 解答 and it was pretty good.

I also checked with some Japanese and my own notes contain more errors than the LLMs output by a large margin.