It's a little difficult to keep track of all the activity happening in the container area. The runC repo's history begins in June 2014? I believe rkt was announced in Dec 2014, right?
It was just a week or two before the announcement. You can see the commit activity here: https://github.com/coreos/rkt/graphs/commit-activity. The earlier blips are standard license files and other boilerplate from a project template used for new repos.
You could be right, I seemed to recall it was started in July. They did move repos around a few times and eventually split the ACI out of the Rkt repo, so perhaps some history was dumped/re-written at some point.
