https://arstechnica.com/gadgets/2019/04/windows-10-may-2019-update-now-available-on-the-release-preview-ring/

For a day or two, members of the Windows Insider Program are in that special limbo period that lets them opt out of the preview program without having to reinstall their operating system from scratch. At the same time, anyone not in the Insider Program can now get early access to the May 2019 update, build 18362.30.

For most of the year, the only way out of the Insider builds is to reinstall the previous stable Windows release. But twice each year, there's a short period where the Fast and Slow rings are shipping the same build as will be used for the stable release of the twice-annual feature updates. During this time, users of the Insider builds can drop out of the Insider program entirely or switch to the Release Preview ring, and their systems will update to the stable release and then stay on the stable track from that point onward.