Old hard drives that show defects are usually deleted and then sent to the manufacturer for repair. We'll get those hard drives back.
Hard disks that can be used again after an intensive technical check are always completely overwritten as part of a new installation before they are delivered to a new customer, for example. This erasure involves zeroing, repartitioning, and formatting.
Hard drives that are defective and no longer electrically addressable cannot be deleted and are disposed of by the certified company "Reisswolf" (https://www.reisswolf-sachsen.de/dienstleistungen/festplattenvernichtung.html).