[collyw]

That's because it comes with a load of built in functionality.

I am sure Flasks documentation is a lot smaller but its essentially just a few parts of Django (it doesn't have a built in ORM from what I understand). Start adding in the documentation for SQL alchemy, documentation for an authentication library and whatever else you need and you will probably start getting something similar but without the guarantee that the pieces will play nicely together.

(Djangos documentation is really good.)