https://wccftech.com/microsoft-sends-windows-10-cumulative-update-to-insiders-for-testing/

Since the Windows 10 1809 update disasters, Microsoft has promised to test the updates it delivers to the users and make better use of its Insider community. The Windows maker has since released a couple of cumulative updates to the Release Preview ring with the new cumulative update now available for the Release Preview ring Insiders.

Microsoft had released a second batch of cumulative updates to various versions of the operating system on March 19 after delivering March 12 updates on last month’s Patch Tuesday. However, this particular update hasn’t yet been delivered to Windows 10 1809 aka the October 2018 Update. Today’s update being sent out to the Insiders might be the March 19 update since the Windows maker had done the same with February’s updates – sending the second batch on March 1. It’s admittedly a little confusing, but that has become the norm since Windows 10 1809 was delivered back in October.