The fact that Apple is pushing an update to iOS isn't particularly newsworthy, that it's doing so for older iPhones and iPads from 2012 and up is something quite different.
There are plenty of Apple devices out there not capable of running iOS 12. Many won't even run iOS 11, but Apple hasn't given up on them yet.
Indeed, a new patch is being pushed to all devices from the iPhone 4s/original iPad mini and above. It fixes a date and time issue that will otherwise negatively impact the GPS location capabilities in those phones and tablets.
The GPS time rollout issue has affected gadgets from many manufacturers and came into effect from 6 April. However, Apple devices won't be affected until 3 November so the patches have been released in plenty of time.
GPS requires requires an accurate time and date reading to work effectively and converts them into a 10-bit week number. Yet a reset of the 10-bit week number due this year means that the tech cannot keep an accurate count beyond the reset date (in November, in Apple's case). Hence the patch.
You will know if your device has been corrected if your iPhone 4s and the cellular versions of the 1st gen iPad mini, iPad 2 and 3rd gen iPad are now on iOS 9.3.6.
If you have an iPhone 5 or iPad 4th gen with cellular, you should now be on iOS 10.3.4.