The title clearly qualifies the claim: "MacOS may lose data _on APFS-formatted disk images_"
I didn't know there were APFS-formatted disk images (new in 10.13). Even when you consider the many different kinds of disk images that macOS supports, there's a pretty clear distinction between disk image and a backup of your startup disk, made to another partition in another drive.
Any additional clarification would get into "MacOS may lose data on APFS-formatted disk images (disk images, not disk-to-disk, as in another volume..." territory.
I didn't know there were APFS-formatted disk images (new in 10.13). Even when you consider the many different kinds of disk images that macOS supports, there's a pretty clear distinction between disk image and a backup of your startup disk, made to another partition in another drive.
Any additional clarification would get into "MacOS may lose data on APFS-formatted disk images (disk images, not disk-to-disk, as in another volume..." territory.