The update is just about the new Kernel and nothing else. There is no apparent UI changes or any new performance improvements and no new Security Patches. Just they might be pushing some prerequisites needed for Pie Upgrade. The Pie Update seems to be around the corner.
It activates the google messages new material design 2 with dark mode.
@user1529438998112 That doesn't have anything to do with this update. The Android Messages Material Design theme is activated by the app's update and not software update. I have been using the app with material design for a month now.