Apple wanted one FS across all devices and ZFS's ARC makes that less than useful in memory-starved phones (and base model Airs amirite?) ZFS's separate cache m

Apple wanted one FS across all devices and ZFS's ARC makes that less than useful in memory-starved phones (and base model Airs amirite?) ZFS's separate cache meant that the better choice was APFS. Once they got around to writing it. And on drives at least, TM backups ARE APFS snapshots.