I've got a stock, non-rooted Nexus 4 which I updated to Jelly Bean 4.3 when the OTA update came out a month or more ago. Just today I got another message that there was a system update available. It said it would update to 4.3, and I double-checked (and took a screenshot), and confirmed I already had it in "About phone."
Nonetheless, I went ahead with the update to get rid of the notification, and it went through the usual process. The before and after screenshots of the about screen confirm that I had the exact same Android, Baseband, and Kernel versions, as well as the same Build Number. I can't find any differences after the update. Does anyone know why this might have happened?
Before screenshot, taken 2013-08-23 16:28:04, before the update was started about a minute later:
After screenshot, taken 2013-08-23 16:36:14 after the update finished and it restarted.