Blastoidea If you encrypt data, then wipe the key(s) how do you ever recover the data?
The whole point of crypto-shredding is that wiping the key is sufficient to make the – still existing – data inaccessible. There is no need to overwrite data (possibly multiple times with different patterns like on floppy disks). But… if the key can be recovered somehow, because it is either still readable somehow/somewhere or can be guessed (bruteforced) the data will be readable again.
If you were using a weak cipher (short key) like, let's say DES (56 bit), recovering the data after fully shredding the key is possible. If an AES 256 bit key is gone there is no known way to access the data afterwards.