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In Azure AD cross-tenant synchronization, synchronized user objects are created as guest objects in the inviting tenant by default. This is because the inviting tenant is considered the guest tenant, and the invited tenant is considered the home tenant.
When a user is invited to the guest tenant, they are given a guest account in that tenant. When the user is synchronized to the guest tenant through cross-tenant synchronization, they are created as a guest object in the guest tenant. This is because the user's home tenant is the invited tenant, and they are only a guest in the guest tenant.
However, the guest objects can be converted to member objects for more information please refer the article Microsoft Entra B2B users be added as members instead of guests.
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Akhilesh.
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