Note that the page you found is for Chromium OS, not Chrome OS, and what happens in Chromium OS doesn't necessarily flow over to Chrome OS at the same release, if at all.
Chromium OS is the open source version of the OS. Google picks up Chromium OS releases on occasion, modifies them, and puts them into the Canary channel. From there, they may be further modified and eventually move to the developer channel. As a elease's code is further refined and QAed, it will move into the beta channel, and then, when all known significant bugs have been fixed, it will be moved into the stable channel, from whence it's gradually rolled out to the Chromebook user base over a period of weeks.
Once the initial transfer from Chromium OS to Chrome OS is performed, no one outside of Google has access to or knowledge of the release.
Having said all that, the page comes as close as you'll find to getting you the answer you want; just don't be surprised when it's sometimes not accurate for Chrome OS.