Microsoft has increased the forced rollout of Windows 1909 to devices running Windows 1809 or earlier so they are unaffected by the approaching end of service for these versions. Microsoft will no longer release quality and security updates for that version of Windows 10. Windows 10 1909 is now available to any user running a recent version of the Windows 10 version. The recommended servicing status is Semi-Annual Channel. Microsoft is performing forced installs of version 1909 so that they continue to be supported. The forced rollout process starts several months in advance of the end of. service date.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-starts-pushing-windows-10-1909-to-more-devices/