Prior to SGOS 7.4.15.1, Administrators didn't have option to disable the NTLM authentication independently from Kerberos Authentication.
Starting from SGOS 7.4.15.1, you can now disable the "Allow NTLM Credentials" option independently of the "Allow Kerberos Credentials" option (Configuration > Authentication > Realms and Domains). This new enhancement provides a straightforward way to enforce stricter authentication policies by ensuring clients use the more secure Kerberos protocol and do not use the less secure NTLM protocol.
Also check: What's new in SGAC 2.2.13