Is this one of the default base attributes in the Okta user profile that can...

Okta has defined 31 default base attributes for all users in an org. These base attributes are generally fixed and cannot be modified or removed. There are two exceptions: First Name and Last Name. These two attributes can be marked as required or optional for Okta and Active Directory (AD)-mastered users. The default setting for new AD instances is that first and last name are required.

https://help.okta.com/en/prod/Content/Topics/Directory/ad-name-optional.htm