Windows 10, versions 1903 and 1909 share a common core operating system with an identical set of system files. Therefore, the new features in Windows 10, version 1909 were included in the latest monthly quality update for Windows 10, version 1903 (released October 8, 2019), but are in an inactive and dormant state. These new features will remain dormant until they are turned on through the “enablement package,” a small, quick-to-install “master switch” that activates the Windows 10, version 1909 features.
The enablement package is a great option for installing a scoped feature update like Windows 10, version 1909 as it enables an update from version 1903 to version 1909 with a single restart, reducing update downtime. This enables devices to take advantage of new features now. For version 1903 devices that receive updates directly from Windows Update, devices automatically get the enablement package by installing the feature update to Windows 10, version 1909.
If a device is updating from Windows 10, version 1809 or an earlier version, this feature update enablement package cannot be manually installed. Instead, it is bundled and automatically included with the feature update to Windows 10, version 1909. Note the installation time is not reduced in this scenario.