HarmBlock AI refers specifically to the content filter on HMD Fuse that prevents nudity from being shown on the screen, shot on the camera, and saved on the device.
HarmBlock+ is the name of the whole service, combining parental control features and the HarmBlock AI content filter. These are managed on the guardian’s device via the HarmBlock+ app and take effect on the linked HMD Fuse phone that your child uses.