Yeah your understanding is spot on, glad that was helpful!

I can imagine platforms choosing to adopt the Kubernetes API for container infrastructure, but it is still the Kubernetes API and it seems like keeping up with changes would be difficult. And there isn't really much in the way of first-class application modeling there, so that's how we ended up with a separate spec specifically for that, with the explicit goal of not being tied to any one implementation.

Something like Swarm or Mesos could implement it, but we're also considering things like cloud PaaS, internal on-prem platforms, and even down to small device runtimes.