Update Confusion - macOS Sierra 10.12.6

On 7/28/2017, I updated my 15-inch 2016 MacBook Pro from macOS Sierra 10.12.5 to 10.12.6. Upon rebooting to complete installation, the App Store app told me that I still had 1 update available. Upon launching the App Store app, that 1 update was for macOS Sierra 10.12.6, despite me having just installed 10.12.6. Here's proof:



So instead of re-installing the 10.12.6 update, I rebooted my machine, thinking that it was mistakenly prompting me to re-install the operating system. Upon reboot, it told me again that I still had 1 update for 10.12.6, so I re-installed the 10.12.6 update. After the 2nd installation and rebooting, it STILL told me that I had a 10.12.6 update available. So at that time, I just ignored the prompting. A few days and a couple of restarts later, my MacBook Pro is no longer prompting me to update to 10.12.6. Couldn't it have gotten things right the first time?