Security update - shirley not
My iPhone says this update "includes over 100 new emoji, introduces eight new wallpapers, and brings other new enhancements and bug fixes for your iPhone."
The only mention of security is the standard phrase they add to every IOS update: "For information on the security content of Apple software updates, please visit this website: https://support.apple.com/HT201222".
That definitely doesn't sound like a security fix to me. Without the El Reg article, I would have assumed this was an optional update that could be safely ignored.