Unlike UFS, ZFS sets the uarch flag automatically whenever a file is modified. The test should be modified to explicitly clear it.
A commit references this bug:
Date: Thu Dec 15 16:13:52 UTC 2016
New revision: 310118
Fix ls_tests:o_flag with ZFS TMPDIR
Unlike UFS or TMPFS, ZFS sets uarch automatically whenever a file is
updated. The test must explicitly clear uarch to be portable across
filesystems. Also, it doesn't need to run as root.
MFC after: 4 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D8741
MFCed to stable/11 by r310118