Following reports that Snapdragon 850-powered Windows PCs, like Samsung's Galaxy Book 2 and Lenovo's Yoga 630 WOS, were being sold with unsupported versions of Windows 10, it appears that Microsoft now supports the Arm-based chip with the April 2018 Update (build 1803).
While Snapdragon 850 support was originally meant for the October 2018 Update, that build (1809) was pulled following an issue that led to deleted files and hasn't been re-released more than a month later. The big fix, it appears, is that the company updated the Windows 10 datasheet. It now lists support for Qualcomm Snapdragon 835 and 850 under Build 1803.
Intel's 9th generation CPUs, however, are still not officially supported. That will occur when the October update re-releases.
It doesn't appear that Microsoft has made any major changes or updates to Windows 10, but we have reached out to Microsoft to ask and will update this post if we hear back.
For now, though, if you have an Snapdragon 850-based laptop, consider it officially supported by Microsoft and Windows 10.