There seems to have been a change at Apple: similar to macOS different versions now seem to be maintained with iOS as well.
What we had already suspected here now seems to be confirmed: Apple only maintained the latest version of iOS in the past – currently iOS 13 – and not any previous version (except for small fixes). But now iOS 12 gets a security update again. A great move of Apple, there are many devices that are still running, but which are denied iOS 13 due to too little memory. Maybe also a small motivation factor was that the Apple support works with relatively old devices itself.
Millions of older devices remain secure.
These devices are for example the iPhone 5s (six years old!), the 6 and also the first iPad Air or an iPad mini 2. To continue using these devices with a safety up-to-date iOS 12 makes absolute sense and it is great from Apple to make this possible. As we recently mentioned HP in a positive way, you have to do this now even more with Apple. After all, millions of devices remain safe to use with this strategy.