acl_trivial(3sec): The definition of trivial ACL is incorrect
manpage - manual pages
Here is defined what is the trivial ACL:
DESCRIPTION The acl_trivial() function is used to determine whether a file has a trivial ACL. Whether an ACL is trivial depends on the type of the ACL. A POSIX draft ACL is trivial if it has greater than MIN_ACL_ENTRIES. An NFSv4/ZFS-style ACL is trivial if it either has entries other than owner@, group@, and everyone@, has inheritance flags set, or is not ordered in a manner that meets POSIX access control requirements.
In reality, the definition defines non-trivial ACL, so the definition is opposite.