Microsoft has not included any major changes in build 18917. We can see the changelog lists more or less the same features included in the first Windows 10 20H1 update.
As the development process is currently in progress, we expect to see more changes in the next build releases.
Albacore shared the details about the new component “Shell Update Agent” on social media.
Here we go
Build 18917 shows first signs of Microsoft's work towards separating the base OS and the shell when it comes to standard desktop Windows
The build introduces a new component called the "Shell Update Agent" which is capable of obtaining and updating the shell on demand
— Albacore (@thebookisclosed) June 12, 2019
Albacore went on to add that one of the features that are based on a Shell package is Action Center in Windows 10.
Action Center seems to be among the first few things that even current builds try to source from a Shell package if available. In case something feels off about AC in future builds, this might be why.
Microsoft introduced a new technique to sync settings in the recent build. Windows 10 can now sync both legacy and advanced features.
Albacore quoted the example of File Explorer configuration. As you can see, Microsoft is silently working on a major new feature.
Another interesting thing related to the shell: It appears that Microsoft is silently working on replacing the current Settings Sync implementation with a new one. The new one should support syncing more advanced and previously “legacy” options such as File Explorer configuration.
If these features pass the testing phase, the changes will be rolled out with Windows 10 20H1 which should land in the first half of next year.
You can download the Windows 10 SDK Preview build to check out the new features.