I had the exact same experience. It's probably the first time I've read something that (besides the images, which I think are pretty obvious) I didn't think was AI. And while I did feel a little tricked learning it was AI, ultimately it was actually just quite good?

I understand why people feel like they need more transparency around these things. Reading for me is intentional, and I feel cheated when I put in the effort to read something for which the author put in little. I would like to think the author put in a lot of effort for this story despite AI assistance, and so it was worth me putting effort in. But whether that's true or not I still felt like I got something out of it (hard not to as a software engineer wondering about their place in the world), and that's something.