mkosi now handles this workaround itself internally.
+++ /dev/null
-# SPDX-License-Identifier: LGPL-2.1-or-later
-
-[Match]
-ToolsTreeDistribution=|!centos
-ToolsTreeRelease=|!9
-
-[Build]
-# The kernel versions in CentOS Stream 9 doesn't support orphan_file, but later versions of
-# mkfs.ext4 enabled it by default, so we disable it explicitly. Except that older versions
-# of mkfs.ext4 don't know about "orphan_file" so we skip it on some tools tree variants where
-# we know "orphan_file" is not supported.
-Environment=
- SYSTEMD_REPART_MKFS_OPTIONS_EXT4="-O ^orphan_file"