Dynamics 365 Business Central (on-premises) 2019 release wave 2 and newer updates are covered by the Modern Lifecycle Policy.
The customer is in full control of its on-premises deployments and must follow this policy. The customer is in control of installing updates in its on-premises environments. Microsoft will support the Dynamics 365 Business Central (on-premises) software as indicated on the Microsoft Lifecycle Policy for Business Central on-premises page, but only if the customer keeps the deployed software current according to this policy. By keeping current, you're getting all the latest feature and bug fixes.
The following image illustrates the update schedule for Dynamics 365 Business Central.
More info: Software Lifecycle Policy and Dynamics 365 Business Central On-Premises Updates
