I don't think most visits to documentation involve reading the summary; they're either looking for a specific detail (which they can find via the index) or for a common snippet that can be expressed in an example.

If I'm using `re` and I check the documentation 20 times over the course of the week, I'll probably read the summary on my first visit, and then on each of the 19 subsequent visits I'll be looking for granular function details or patterns that I can copy. I think it makes sense to put the most frequently-used stuff at the top. The summary will probably be denser and harder to skim than the examples anyway.

I suppose it really depends though. What you want is to get a bit of everything before the break, so that the user can see a couple intro sentences, a few examples, the index (ideally in a sidebar), and the beginning of the overview before they even have to scroll.