Explanation:

Reference:
https://docs.microsoft.com/en-us/azure/storage/files/storage-files-identity-ad-ds-assign-permissions?
tabs=azure-portal
Azure Files supports Azure Active Directory Domain Services (Azure AD DS) authentication for SMB access, allowing you to use your existing Active Directory (AD) identities and groups to control access to Azure file shares.In this scenario, the configuration snippet shows that the storage account (storage1) is using Active Directory (AD) authentication through azureFilesIdentityBasedAuthentication with directoryServiceOptions: "AD".
According to Microsoft Azure documentation, the Storage File Data SMB Share built-in roles (Reader, Contributor, Elevated Contributor) can only be assigned to Azure AD users, groups, or service principals, not to computer objects.
Statement 1: # User1 is an on-premises AD user synchronized to Azure AD. Since Azure Files uses identity- based authentication through AD, User1 can be assigned roles like Storage File Data SMB Share Contributor to access share1.
Statement 2: # Computer1 is a computer account and cannot have Azure RBAC roles directly assigned in Azure. Therefore, you cannot assign SMB Share Reader to it.
Statement 3: # User2 is an Azure AD user (cloud-only identity). Azure RBAC roles for storage shares can also be assigned to Azure AD users. Hence, you can assign Storage File Data SMB Share Elevated Contributor to User2.