SSDs don't cycle blocks based on how much you've written. You can write over the entire reported capacity of a drive 100 times and there's still the chance, how

SSDs don't cycle blocks based on how much you've written. You can write over the entire reported capacity of a drive 100 times and there's still the chance, however small, that your encryption key and some encrypted data are still sitting around on some chip. You just can't guarantee that it's gone. For all you know, the controller has marked them as bad and isn't going to reuse them, even though there's still recoverable data on them. Since there's no way to reach them through the drive interface, there's also no way to erase them. But if someone opened up the drive and pulled the chips, there they would be.