Do you take down all of your projects and then bring them back up at the new version? If not, then you have times at which the change is only partially complete.
Nah, these days the new thing is Vibe Deployments, just ship the change and pray.
People that Blue Green are doing that, aren't they?
Canary/Incremental, not so much
I would see a potentially more liberal use of atomic, that if the repo state reflects the totality of what I need to get to new version AND return to current one, then I have all I need from a reproducibility perspective. Human actions could be allowed in this, if fully documented. I am not a purist, obviously.