I just found out that the mark as authoritative options in the Portal for ArcGIS is limited to the Portal administrators. I have been reading some other information and I get that it can be reasonable that not all can set this value, especially on AGOL. In our organization, we have a clear separation between the data owner and the organization that maintain and manages the Portal. A data owner is not allowed to have admin privileges, this comes by the reason that we have many departments some with higher security requirements.
If a user is given any administrator privileges in the Portal this becomes translated as administrative privileges of all federated GIS Server. In other words they get access to all published services. This is another topic, but I can’t get why and would like to see a better separation of portal and server administrative privileges in the future.
I would like to suggest that a general privilege becomes implemented for roles like an organization data provider, including the ability to “mark as authoritative”.