It's not an older driver, it's today's driver, this is a different branch. Newer versions number doesn't always indicates newer, it's depending on the branch. For example when the 378.49 came out, the HD audio driver and Experience included packages where already outdated. This is 02/24/2017, 21.21.13.7698 .. while your mentioned driver is 02/23/2017, 21.21.13.7877 .. the last number only indicate the internal compiled tree. And of course there are different since there exist legacy, game and Vulkan ones. The Vulkan Runtime Libaries are also now 1.0.42 (from yesterday compiled).