Are you using Salesforce's SAML JIT provisioning where a user account is created at the time of sign-in, or are you using the Azure AD User Provisioning feature under the "Provisioning" blade of a Salesforce Enterprise Application in Azure AD? It isn't clear which you are using.
If you are using SAML JIT, your question would likely be better handled by Salesforce - our service would merely provide a SAML token/assertion as configured in the SAML SSO setup in Azure AD. How that data is consumed by Salesforce to either sign in a user or potentially create a user is logic entirely owned by Salesforce.
If you are using Azure AD User Provisioning - these issues can be far more complex (and contain more personal data about the users being provisioned) than should be handled over a Microsoft Q&A post - and in that case I would strongly suggest creating a support case with Azure AD to receive assistance there.