This update includes quality improvements. No new operating system features are being introduced in this update. Key changes include:
According to ZDNET, This Windows 10 Patch was for AMD's new Microcodes update that will be coming soon in BIOSes updates.:Windows 10 on AMD? This new update plus Microsoft's patch block Spectre attacks | ZDNet
Does Windows 10 v1803 also fix BIOSes?
I far as I know everyone not in the Preview Program doesn't have Windows 10 v1803. Besides, this update was probably included in Windows 10 v1803 but since no one in the general public have version 1803 the Post still is relevant. Besides, not everyone is going to upgrade to the new version.
Windows has some workarounds and as for a BIOS that is up to the motherboard/machine vendor
This Windows update is to prepare Windows for when AMD releases the new Microcodes to the motherboard manufacturer's so that they can update the BIOS for a new BIOS release.
My post was strictly FYI Only and nothing more.