APFS disks don’t launch the house for deleted information instantly. The information will nonetheless exist in an APFS snapshot, which information the state of the disk at a cut-off date.
Snapshots will probably be deleted after 24 hours; or after the disk is backed up by Time Machine. The house could also be recovered by the file system if wanted for brand new information.
The Terminal command:
tmutil listlocalsnapshots /
will checklist all of the snapshots saved on the drive.
tmutil deletelocalsnapshots /Volumes/Name_of_disk
will take away them.
Nonetheless, the snapshots’ measurement is normally proven as “Purgeable”, so I do not know why you are seeing Zero Purgeable house.