I think the closest thing I can find is in the Identity Awareness R80.20 Admin guide where it says:
"Enter the Active Directory credentials and click to verify the credentials.
Important - For AD Query you must enter domain administrator credentials. For Browser-Based Authentication standard credentials are sufficient."
So, I would read that to mean the default requirement is an admin (or domain admin) account unless you wanted to create a user with custom permissions (without domain admin) as illustrated in the sk article I referenced.
Here's a direct link to that portion of the admin guide for your AD administrator's reference. It should be under the section titled "Enabling Identity Awareness on the Log Server for Identity Logging"
R80 CCSA / CCSE