Anyone who upgrades an iPhone or iPad to iOS 12.2 can’t change their mind. Apple ceased digitally signing the previous version so it can’t be installed anymore.
This is normal. Apple always stops allowing people to downgrade a few weeks after a newer iOS version is released.
Jumping up or down an iOS version requires a copy of the replacement operating system that’s been “signed” by Apple. Otherwise, the iPhone or iPad will refuse to install it.
Apple continues to approve installations of the older version for a short time because major bugs are occasionally found in new releases, and many people might need to downgrade. But iOS 12.2 has been out for long enough that it’s not going to suddenly start crashing everyone’s handset.
As of today, Apple stopped signing iOS 12.1.4, a version introduced in February. It had already stopped approving the installation of all other previous interactions.
Recently, there was evidence Apple was going to stop allowing downgrades. But it seems this was just a bug, not a feature.
The debate over upgrading
Moving to the latest iOS version is a surprisingly controversial topic. Installing iOS 12.2 brings new features, like additional Animoji and patches for security flaws, but there’s evidence that it might come with a battery hit.
A recent study on an an older iPhone model found that a version of iOS 10 provided a significantly longer battery life than iOS 11 or iOS 12. That said, the study also found that both iOS 11 and iOS 12 used approximately the same amount of power.