This happens because of ACL created on sp_log.sys_created_by.

There is OOB ACL to do restrict the read operation

https://<instancename>.service-now.com/sys_security_acl.do?sys_id=6aec9a655302111066c1ddeeff7b1288

This is meant to be not seen by any body including admin (admin override is false).

Try modifying it as per need