Hi,
oVirt node ng is shipped with a placeholder rpm preinstalled.
The image-update rpms obsolete the placeholder rpm, so once a new image-update rpm is published, yum update will pull those packages. So you have 1 system that was a fresh install and the others were upgrades.
Next, the post install script for those image-update rpms will install --justdb the image-update rpms to the new image (so running yum update in the new image won't try to pull again the same version).
Regarding the 4.1.6 it's very strange, we'll need to check the repos to see why it was published.
As for nodectl, if there are no changes, it won't be updated and you'll see an "old" version or a version that doesn't seem to be matching the current image, but it is ok, we are thinking of changing its name to make it less confusing.
Hope this helps,
Yuval.