That's basically right. That change in focus is usually set off by the kiriji, the cutting word. But it doesn't have to take place before the last line, it could be near the beginning. It's not necessarily a surprise or an inversion, it is just usually a change in focus. I gave some examples in my post explaining haiku here.
I also covered in that post a little of what you are talking about. Haiku as it original was was highly influenced by Zen. It inherited the idea that we can often describe reality better by saying less. The more you try to explain, the less you do, the more words you use, the more complicated you make it, and so on. The challenge of haiku then is deleting everything except what is essential.
See the issa snail haiku on that post I wrote. I think that illustrates the difference quite well. Look at how sparse the Japanese really is but yet how it can suggest so much. That is one of Issa's most famous haiku and one of the most famous in Japan and for good reason.
I remember reading that post when you published it. I’ll take a look at again sometime today.