[heavenlyhash]

I heartily agree with your sentiment "rollback one of those inherently complex ideas" :) It's true that sometimes it's not even well-defined, such as for database migrations.

Some of this also depends on context. If I'm shipping a single primary deployment of a massive fairly monolithic SaaS product, I can do this time-marches-on stuff. If I'm actually shipping shrinkwrapware -- and as a sibling comment says, doing rolling blue-green deploys also looks like this, if briefly -- switching something back to a previous code version is very worth minding.