> Nothing is permanently deleted unless they used a shredding software, and even then
Where did you get that idea? As soon as a disk cluster is freed it can be filled with other data.
Some data remains when deleted but it’s completely unreliable. What do you think happens when you fill a disk, delete 10% of it, and fill that part? You think the old data is still around?
Its there, the magnetic domains are not completely gone. They are just reduced in number so they are below the normal drive’s detection threshold. Specialized equipment can recover it.