As mentioned in [1], AzureAD returns a link to a service to get groups.
(Please see the example of Attribute [2])
We need a feature to access Groups Overage Indicator link and parse a response to get actual groups in SAML adapter.

[1] https://learn.microsoft.com/en-us/azure/active-directory/develop/reference-saml-tokens

[2]

    <Attribute Name=" http://schemas.microsoft.com/claims/groups.link">
        <AttributeValue>
            https://graph.windows.net/\{tenantID}/users/\{userID}/getMemberObjects
        <AttributeValue>
    </Attribute>