The Raw and the Business Data Vault Foundation Layer can be built at different speeds.

The Raw Foundation Layer is a technical implementation based on source systems and only requires a source analysis and is a direct representation of the source.

The Business Data Vault is a business based implementation that requires functional and technical analysis to understand business requirements.
New business concepts can be created (New Hubs) but implementation experience show typically link tables between existing Source Business concepts (source based Hubs) support requirements for 90%.

The multiple speed approach supports better functional and technical analysis when the raw data vault data is already available.