“This does not mean that Google is making Android a closed-source platform, but rather that the open-source aspect will only be released when a new branch is released to AOSP with those changes, including when new full versions or maintenance releases are finished.”
Google is moving all Android development behind closed doors and will publish code only at release. It insists Android is still open source. Custom ROM projects and outside developers lose the view of work in progress. Open source now means a code dump after the fact.