There has been a huge amount of work done on Linux over the years to increase parallelism in the VFS and in the common filesystems like ext4, XFS and btrfs. I

There has been a huge amount of work done on Linux over the years to increase parallelism in the VFS and in the common filesystems like ext4, XFS and btrfs. I would guess that macOS, being targeted at desktops and the typical workloads being run on them, hasn't received the same level of scrutiny in this particular area.