Btw, here is what it says online..
To correctly set do_ldap_fetch and do_internal_fetch parameters for SAML, you should set do_generic_fetch to false if using an on-premises LDAP directory to use the SAML identity provider for fetching user attributes, and set do_internal_fetch to false if you are not using an on-premises LDAP and instead rely solely on the identity provider. The key is to disable the general fetch or the internal fetch to ensure the SAML information is the primary source for user data.
Best,
Andy