these were updates, pretty sure that 1903 is officially out just not rolling out to the masses or GA yet. Been running is for more than a month without issues.
All new 1903 updates: https://forums.mydigitallife.net/threads/windows-10-hotfix-repository.57050/page-398#post-1523767 Check the RTM in the dotnetcu
Because after the last QU v1809 mess, MS isn't taking any chance that might lead them to another disaster and criticism, which is a good move IMO.
With each "new version" of windows 10 I understand less than those of Microsoft, it is assumed that this version 1903 is "RTM" sent to Developers vis MSN, however it is still named as an Insider Build for Patches or System Updates
VMware Workstation Pro 15.1.0 build-13591040 has been released, together with updates to other VMware software. Initial impressions: problems seem to have been fixed.