I get this feeling about Django, but not about Flask. Its codebase is so lean I can read all the relevant parts in an hour when I want to get back into it. I don't even need docs for this thing.
However, I understand what you mean about request / response, I don't like how this is handled in most python frameworks actually, it's usually too much abstracted away.
The nicest (imperative) environment for asynchronous execution I've seen is Objective C/Cocoa for some reason. It has a way of showing you all the handles you might need, but it also makes it fairly obvious when and how these handles are called. Together with lambda support ('blocks') it's simple but effective.
I think the main difference is enterprise + closed source + well documented environments vs. opensource + not so well documented environments often originating from someone's hobby. When it comes to big middleware frameworks I prefer the first, but small lean stuff such as Flask is just fine to use IMO.
My advice is to not rely too much on the docs when you want to really know something - take a look at the source, it's all there.
I am getting turned off left right and centre by frameworks - Django and even Flask just make reasoning about the request/response more difficult.
Maybe I don't know how to use this but ... It would take me three months to read the new Django docs.
I am not a hater here, just wanting the simple life