While blog posts aren't ideal they're (like you point out) better than nothing. But blogging goes completely against the grain of how Apple operates internally. The WebKit blog is a singular notable exception because that's a highly visible Open Source project. Even the free-form Q&A portions of WWDC sessions are rarely as frank as they should be in terms of usability.

No blogs is fine, that's just the corporate culture, but no blogs and no good up to date architectural documentation is a huge problem. It leads to cargo-cult understanding or complete misunderstandings by outside developers. Hell, it leads to cargo-cult understanding by internal developers.