You are correct, since you are using AD/DNS there is no need to use NetBios name service. I was not able to find some document or article for further clarification but you can check the below documentation:
As for the settings ( is-netbios-over-tcp-enabled & is-nbns-enabled) is set to either false or true per vserver (svm).
In the example provided, vserver svm1 have the is-netbios-over-tcp-enabled setting set to true which is enabled and the "is-nbns-enabled" setting set to false which is mean is not enabled. The vserver svm2 has the options set the opposite.