Microsoft has started testing the new Windows 10 Controlled Feature Rollout feature with Windows Insiders in the Slow ring. This feature allows Microsoft to slowly roll out new features without releasing entirely new builds. Using this feature Microsoft can ship builds with disabled features that are gradually enabled by Microsoft to small groups of users. At this time there is no known policy or method that can be used to control CFR or even disable it entirely. Microsoft has asked for more information when the feature was first announced, but was told there was no further information available at the time.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-begins-testing-windows-10-controlled-feature-rollout/