Em, no - that can only be done in internal store "data" directories which are usually formatted with UNIX filesystems and are by default secure (and cannot be accessed by other apps at all).
WhatsApp is storing to external (on most devices FAT) storage (which was SD card on older devices, it's usually a separate directory/partition on newer ones) which does not have any ACL-like system due to FAT backwards compatibility.
WhatsApp is storing to external (on most devices FAT) storage (which was SD card on older devices, it's usually a separate directory/partition on newer ones) which does not have any ACL-like system due to FAT backwards compatibility.