Data Connect grants a more granular control and consent model: you can manage data, see who is accessing it, and request specific properties of an entity. This enhances the Microsoft Graph model, which grants or denies applications access to entire entities.
Microsoft Graph Data Connect augments Microsoft Graph's transactional model with an intelligent way to access rich data at scale. The data covers how workers communicate, collaborate, and manage their time across all the applications and services in Microsoft 365.
Reference:
https://docs.microsoft.com/en-us/graph/data-connect-concept-overview