Sure, but the thread was about learning and the GP referenced learning several times. So in this context, it was a learning project, and it sounds like a great one.
It's good that you added those details. Your original comment was a shallow dismissal, which breaks the site guidelines (not good) but the details are substantive and interesting (much better). Still, even the edited comment comes across as a cross-examination, as if you're dressing someone down for putting a lot of time and work into something creative. That's a buzzkill for everyone here. I'm sure you didn't intend it that way, but intentions get lost. We have to be careful not to let HN turn into a place where people won't share what they're doing because they get such a hostile reception (see https://news.ycombinator.com/item?id=18705345).
Your comment would be better if instead of leading with a mean insult, you made clear that you were thinking about whether it would work as a product and realized some issues with that. Also, if you think about it, asking whether someone's hobby project is intended as a product prototype is actually a high compliment to the hobby project. There should be no problem framing that positively. Had you done so, you'd probably have gotten a bunch of replies exploring the issues you raised, and maybe even the creator would have found something to respond to. The goal of HN threads is interesting conversation, and that would have been a much better vector to get there.