If i'm not wrong, but far as i remember Windows Vault is just the service with the location where the credentials are stored, and the Credential Manager is the frontend of the Windows Vault, since is not an Service but rather an GUI application that utilizes the Windows Vault service for his operations.

Credential Manager indeed uses different approaches to store credentials in the OS (somehow, microsoft did it this way). I may be wrong but Windows has some services that doesn't work entirely alone and look like are the same, but they really aren't.