I think you were right to think that he should have posted a new question. Indeed, if he had not deleted it, I would have rolled back his edit and advised him to post his new problem separately.

I don't think you were right to assume he knows how the site works, even after eight years. Since he doesn't have very much reputation, it could be that he doesn't actually spend a lot of time here. He does, however, spend quite a bit of time at Stack Overflow, and perhaps he knows how that site works. As far as I know, they also would not accept this sort of situation and would expect separate questions. I could be wrong about that, though.

I think you were right to think that he should have posted a new question. Indeed, if he had not deleted it, I would have rolled back his edit and advised him to post his new problem separately.

I don't think you were right to assume he knows how the site works, even after eight years. Since he doesn't have very much reputation, it could be that he doesn't actually spend a lot of time here. He does, however, spend quite a bit of time at Stack Overflow, and perhaps he knows how that site works. As far as I know, they also would not accept this sort of situation and would expect separate questions. I could be wrong about that, though.

Based on the user's further activity, though, I suspect he deleted the question because he thought he figured out his new issue himself, and decided to move on. Then realized he hasn't, and posted a new question. When you see the new question, you'll have to decide for yourself whether to bother putting in any effort answering it.