I don't believe one is "identified" by NT AUTHORITY\SYSTEM. NT AUTHORITY and SYSTEM are not accounts or groups. User accounts contribute their SID as the primary SID to the access token but the access token can contain other SIDs, most utilities reflect the principle SID but when a permission is required windows will look for any SID that has the required permission associated to that token.

The SID only defines a set of permissions, it doesn't need to define users or groups. NT AUTHORITY\SYSTEM can be added to accounts to become the principle SID for those accounts, and will show up in task manager as SYSTEM for tasks that have it as their principle SID. but a user this is not.

I don't believe one is "identified" by NT AUTHORITY\SYSTEM. NT AUTHORITY and SYSTEM are not accounts or groups. User accounts contribute their SID as the primary SID to the access token but the access token can contain other SIDs, most utilities/tools reflect the principle SID in outputs and such but when a permission is required windows will look for any SID that has the required permission associated to that token.

The SID only defines a set of permissions, it doesn't need to define users or groups. NT AUTHORITY\SYSTEM can be added to accounts to become the principle SID for those accounts, and will show up in task manager as SYSTEM for tasks that have it as their principle SID. but a user this is not.