It looks like Microsoft are testing a new space saving feature for Windows 10. I didn’t spot it in any release notes but currently testing in the latest Windows Insider dev build (20201) is a new option to Archive apps. The feature is turned on by default and automatically archives apps that are not used. It retains the files and user data but offloads the application files, and then when you need the app it will automatically downloads them down from the Microsoft Store restoring the app.
This a feature that iOS has already and seems an effective way of keeping devices clean and avoid unused apps taking up all your disk space.
Just because the Microsoft are testing the feature it doesn’t mean it will come to any specific release of Windows 10 as Microsoft use the Dev Channel to test feature currently in development and not tied to a release.