It can discard with the proper SD commands (use `--discard`), if your SD adapter supports that. So not with USB card readers, but with many built-in SD card slots. The main reason to use this formatter instead of the OS built-in formatter (or mkfs) is that this creates the correct type of file system (FAT or exFAT depending on card size) and uses correct allocation sizes etc. for devices expecting a factory-formatted card.