The title is slightly misleading but not entirely. Docker was, at first, a container technology. However, after it received its funding it has tried to convince the community and investors that it can be more and started to provide container orchestration tools, i.e Swarm, Machine and so on. Docker has received most of its momentum and attention because of the work they did around the container format. Docker build, run, stop, encapsulates most users experience of Docker.

Docker wants to be known as a platform providing container management tools and it needs to do this quickly because Mesosphere and Kubernetes provide this type of functionality at a more mature level, albeit using somewhat different philosophies. The container format part of Docker is ultimately replaceable.

Google (Ventures) backing Tectonic is significant because Tectonic will provide a commercial enterprise-ready distribution of Kubernetes supporting Rocket. Rocket doesn't need to reach feature-parity with Docker to be a notable replacement because Docker already does too much. All Rocket needs to do is provide the much needed enterprise features that Docker is lacking and integrate well with Mesosphere or Kubernetes. If this happens before Swarm and Machine mature, we could be wondering 6 months down the road what the hype around Docker was all about.

If Tectonic succeeds in the enterprise marketplace then Google will have stealthily marginalised Docker using community efforts through rkt and kubernetes and not had to fight them directly.