No problem about the delay, of course.
I put on better glasses, and guess what? There is a Container management section in the XO docs after all, in docs/xo5/manage_infrastructure.md.
It doesn't describe the old xscontainer route though. It says you can run Docker inside a VM, then links out to Docker's own docs and the Kubernetes recipe, so there's no procedure sitting there to walk anyone into a wall, and no sign of the feature either.
On the features matrix I can't check it the way I checked the rest, because the page builds itself in the browser and fetching it gives me nothing, so treat that one as unchecked rather than confirmed.
The Feeder entry still isn't there, I looked again today, so that part stands.