More of an observation than anything, but Docker certainly has the corporate-ese marketing speak down pat. Much more so than most other "hot" OSS/platforms. Why such a different culture? Or are they just trying to climb into VMWare's bed?
The comment you're replying to didn't say it wasn't useful for the "average start-up with at most a couple of Rails apps" - it said it's less useful ("not nearly as much of a value-add") compared to a large enterprise.
When your entire environment runs on half a dozen VMs you have much less to gain by faster/easier provisioning then when you're running tens of thousands.
FTFY.