A cloud-based identity and access management service for securing user authentication and resource access
The tokens used in Azure AD Provisioning need to be issued by the SCIM application. The token flow that you are mentioning is OAuth 2.0 Client Credential Grant flow, in this case using Azure AD as the issuer of the tokens. Custom non-gallery applications do not support OAuth 2.0 at this time and require long-lived bearer tokens. Given that, using short-lived OAuth 2.0 access tokens, whether issued from Azure AD or another OAuth server, will not work.