Apparently they must be rolling this feature out differently than other features which trickle down the channels. Maybe Google Now have been in the channels for a while without anybody knowing, just disabled unless some flag was enabled by either the client or a server. This way they can enable it for only certain users, circumventing the normal Channel release cycle.

I found this interesting quote in a 2014/02/03 blog post[1] on the Google Chrome blog:

"Update 3/24/2014: Starting today and rolling out over the next few weeks, Google Now users in all languages will be able to get these notifications in all channels of Chrome. To enable this feature, simply sign in to Chrome with the same Google Account you’re using for Google Now on Android or iOS."

This also suggest that they are using a different release approach than just relying on the release-channels.

[1] http://chrome.blogspot.com/2014/02/get-notifications-from-go...