This is nothing to do with kerberos. You do not need kerberos to use NFS version4 shares in either Linux or FreeBSD.
The reason chmod fails is because you’ve picked NFSv4 style ACLs for your dataset and how SCALE sets the values of the related dataset properties of aclmode and aclinherit when the acltype is NFSv4.
For example. see here.
Please review docs here.