Microsoft has started testing the throttled delivery system with Windows Insiders in the Release Preview Ring and Windows 10 19H2 Build 18363.327 is now rolling out to a small number of users today. Microsoft is also using Controlled Feature Rollout (CFR), which means not every user will have access to the new features initially. Microsoft hopes to test new features gradually in order to determine their reliability. The update is not the final version that will roll out to all users later this year.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-starts-testing-throttled-rollout-of-windows-10-19h2/