setfacl(1) doesn't state anywhere that ZFS supports only NFSv4 ACLs. It should be mentioned.
Hm, but it's not true - NFSv4 ACLs are also supported with UFS, when mounted with nfs4acls option, and NFSv4.
(In reply to Edward Tomasz Napierala from comment #1)
I think you have the claim backwards: it's that the only ACL type that can work with ZFS is NFSv4 (not that the only fs that can be used with NFSv4 is ZFS).